Russian troops launched their anticipated attack on Ukraine on Thursday, as President Vladimir Putin cast aside international condemnation and sanctions.

Here’s the latest on the Ukraine-Russia conflict:

• Russian military claims to have knocked out Ukraine’s air defense assets and airbases.
• Ukrainian military reported that it has shot down five Russian aircraft while fending off the Russian attack on the country.
• Ukraine President Volodymyr Zelenskyy has declared martial law and urged citizens to stay home and not to panic as Russia launches its military strike.
• Ukraine’s president and U.S. President Joe Biden spoke early Thursday after the “unjustified attack by Russian military forces” began, Biden said.
• Big explosions were heard in Kyiv, Kharkiv, Odesa and other areas of Ukraine.

The Russian military says it has knocked out Ukraine’s air defense assets and airbases.

The Russian Defense Ministry said the Russian strikes have “suppressed air defense means of the Ukrainian military,” adding that the infrastructure of Ukraine’s military bases has been incapacitated.” It denied the claims that a Russian warplane was shot down over Ukraine.

The Ukrainian military, meanwhile, reported that it has shot down five Russian aircraft while fending off the Russian attack on the country.

Russian President Vladimir Putin announced that he unleashed an attack on Ukraine in a televised address early Thursday, drawing international condemnation.

Putin announced a military operation in Ukraine and warned other countries that any attempt to interfere with the Russian action would lead to “consequences they have never seen.”

Big explosions were heard before dawn in Kyiv, Kharkiv and Odesa as world leaders decried the start of a Russian invasion that could cause massive casualties and topple Ukraine’s democratically elected government.

Ukrainian President Volodymyr Zelenskyy introduced martial law, saying Russia has targeted Ukraine’s military infrastructure and explosions are heard across the country. Zelenskyy said he had just talked to President Joe Biden and the U.S. was rallying international support for Ukraine. He urged Ukrainians to stay home and not to panic.

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Putin said the attack was needed to protect civilians in eastern Ukraine – a claim the U.S. had predicted he would falsely make to justify an invasion.

In a televised address, Putin accused the U.S. and its allies of ignoring Russia’s demand to prevent Ukraine from joining NATO and offer Moscow security guarantees. He said Russia’s goal was not to occupy Ukraine.

A full-blown Russian invasion could cause massive casualties and topple Ukraine’s democratically elected government. And the consequences of the conflict and resulting sanctions levied on Russia could reverberate throughout the world, affecting energy supplies in Europe, jolting global financial markets and threatening the post-Cold War balance on the continent.

He said the Russian military operation aims to ensure a “demilitarization” of Ukraine. Putin urged Ukrainian servicemen to “immediately put down arms and go home.”

Explosions reported in several parts of Ukraine

A CNN team in the capital Kyiv reported explosions coming from the direction of the international airport, around 15 miles east of the center of Kyiv. Social media accounts reported several explosions in the Boryspil area to the east of the capital, where the international airport is located.

CNN has not confirmed that the airport has been targeted.

A CNN team in Kharkiv, the second-largest city in Ukraine located in the country’s northeast, heard a “steady stream of loud explosions.”

Video above: Flashes seen in Kyiv before dawn

A team in Odessa heard two groups of explosions about 20 minutes apart, and another team in southeastern Zaporizhzhia, which lies on the Dnieper River that cuts through the country, heard at least one very distant explosion. Two people in Kramatorsk told CNN that they have heard at least two massive explosions in the early hours of Thursday.

Before Putin’s address, Russia issued a notice banning civil aircraft from flight routes bordering north-eastern Ukraine. Separately, Ukrainian aviation authorities issued a notice restricting Ukrainian airspace in the regions around the capital Kyiv, Dnipro, Lviv, Odessa and Simferopol.

European aviation regulators said there is a “high risk” to civilian aircraft near the Ukrainian border, fearing they could be targeted on purpose at any altitude.

“Air operators are reminded that this is now an active conflict zone,” said the European Union Aviation Safety Agency, known as EASA.

Video above: Air raid sirens heard in Kyiv

Biden denounces ‘unprovoked’ attack on Ukraine

Biden denounced the “unprovoked and unjustified” attack on Ukraine and said the world will “hold Russia accountable.”

“The prayers of the entire world are with the people of Ukraine tonight as they suffer an unprovoked and unjustified attack by Russian military forces,” Biden said in a statement. “President Putin has chosen a premeditated war that will bring a catastrophic loss of life and human suffering. Russia alone is responsible for the death and destruction this attack will bring, and the United States and its Allies and partners will respond in a united and decisive way. The world will hold Russia accountable.”

Biden said he planned to speak to Americans on Thursday after a meeting of the Group of Seven leaders. More sanctions against Russia were expected to be announced Thursday.

Ukraine ambassador at UN: Putin has ‘declared war on Ukraine’

Ukraine’s ambassador at the United Nations has told the Security Council that Russian President Vladimir Putin has “declared war on Ukraine.” He also pressed his Russian counterpart to state that Russia will not shell and bomb Ukrainian cities.

Ukrainian Ambassador Sergiy Kyslytsya said Wednesday night that if Russian Ambassador Vassily Nebenzia was not in a position to give a positive answer, he should relinquish the presidency of the Security Council, which Russia holds this month.

Video above: People praying in the street in Kharkiv, Ukraine

The Ukrainian then asked for another emergency meeting of the Security Council, calling on the U.N. body “to stop the war because it’s too late to talk about de-escalation.”

Kyslytsya then asked if he should play the video of Putin announcing military operations being launched in Ukraine.

Nebenzia replied: “This isn’t called a war. This is called a special military operation in Donbas.”

Ukrainian president rejects Moscow’s claims

The Ukrainian president rejected Moscow’s claims that his country poses a threat to Russia and said a Russian invasion would cost tens of thousands of lives.

“The people of Ukraine and the government of Ukraine want peace,” Zelenskyy said in an emotional overnight address, speaking in Russian in a direct appeal to Russian citizens. “But if we come under attack, if we face an attempt to take away our country, our freedom, our lives and lives of our children, we will defend ourselves. When you attack us, you will see our faces, not our backs.”

Zelenskyy said he asked to arrange a call with Russian President Vladimir Putin late Wednesday, but the Kremlin did not respond.

In an apparent reference to Putin’s move to authorize the deployment of the Russian military to “maintain peace” in eastern Ukraine, Zelenskyy warned that “this step could mark the start of a big war on the European continent.”

“Any provocation, any spark could trigger a blaze that will destroy everything,” he said.

He challenged the Russian propaganda claims, saying that “you are told that this blaze will bring freedom to the people of Ukraine, but the Ukrainian people are free.”

Other leaders condemn Putin

At an emergency meeting of the U.N. Security Council called by Ukraine because of the imminent threat of a Russian invasion, members still unaware of Putin’s announcement appealed to him to stop an attack.

U.N. Secretary-General Antonio Guterres opened the meeting, just before the announcement, telling Putin: “Stop your troops from attacking Ukraine. Give peace a chance. Too many people have already died.”

NATO Secretary-General Jen Stoltenberg issued a statement saying he strongly condemns “Russia’s reckless and unprovoked attack on Ukraine, which puts at risk countless civilian lives. Once again, despite our repeated warnings and tireless efforts to engage in diplomacy, Russia has chosen the path of aggression against a sovereign and independent country.”

Anxiety about an imminent Russian offensive soared after Putin recognized the separatist regions’ independence on Monday, endorsed the deployment of troops to the rebel territories and received parliamentary approval to use military force outside the country. The West responded with sanctions.