Despite sanctions and warnings of a humanitarian crisis, Moscow launched a fresh assault on a residential block in Ukraine's second city of Kharkiv as the US leader sought to steel the American public's resolve for the turmoil ahead.

"A Russian dictator, invading a foreign country, has costs around the world," Biden told lawmakers in his annual State of the Union address, promising "robust action to make sure the pain of our sanctions is targeted at Russia's economy."

Biden had planned to tout his policy successes during his speech, discuss how the United States had turned a corner on the pandemic and outline what he wanted to accomplish in the coming months.

But much of that was upended by one of the most significant geopolitical crises since the end of the Cold War, as Putin's nuclear saber-rattling sent shockwaves through the international community.

In an emotional start to Biden's address, lawmakers packed into the US Congress gave a standing ovation to the Ukrainian people as the president voiced solidarity with the ex-Soviet country.

Speaking on day six of Russia's invasion, Biden said Putin's aggression was "premeditated and totally unprovoked" -- but hailed the resolve of the Western alliance in responding with brutal sanctions.

"(Putin) thought he could divide us here at home," Biden said. "But Putin was wrong. We are ready."

Biden said he had tasked the Department of Justice with assembling a task force to go after the "crimes" of the Russian oligarchs "to find and seize their yachts, their luxury apartments their private jets."

"We are coming for your ill-begotten gains," he promised.

"And tonight I am announcing that we will join our allies in closing off American air space to all Russian flights -- further isolating Russia and adding an additional squeeze on their economy."

Earlier Biden had spoken on the phone to Ukrainian President Volodymyr Zelensky, who accused Moscow of "state terrorism" over the bombardment of Kharkiv.

Although Russia has denied targeting civilian infrastructure, British Prime Minister Boris Johnson called the assault "absolutely sickening" and reminiscent of massacres of civilians in Sarajevo in the 1990s.

- 'Shattered peace' -

Eight people were reported dead in a residential building in the city and officials said 10 had been killed by Russian shelling on a local government complex.

A strike on the main TV tower in Kyiv also killed five people and knocked out some state broadcasting, Ukrainian officials said, but left the structure intact.

Fresh explosions were heard late Tuesday in Kyiv and Bila Tserkva, 50 miles (80 kilometers) to the south, according to local media.

News outlets also reported Russian missiles damaging residential buildings and a hospital in Zhytomyr, citing the major transport hub's mayor Sergei Sukhomline.

The International Criminal Court has opened a war crimes investigation against Russia. Ukraine says more than 350 civilians, including 14 children, have been killed in the conflict.

In southern Ukraine, the city of Mariupol on the Azov Sea was left without electricity after bombardment, while Kherson on the Black Sea reported Russian checkpoints encircling the city.

In a key victory for Moscow, Russia's defense ministry said its troops had linked up with pro-Moscow rebel forces from eastern Ukraine along the Azov Sea coast.

But Ukrainian forces say despite incursions by "sabotage groups," Russian forces have yet to capture a major city.

During a visit to an airbase in Poland, NATO chief Jens Stoltenberg said Putin had "shattered peace in Europe."

Zelensky meanwhile reiterated an urgent appeal for his country to be admitted to the European Union.

More than 660,000 people have fled abroad, the UN refugee agency said, estimating that a million people are displaced within ex-Soviet Ukraine, which has a population of 44 million.

- 'All-out assault' -

Russia has defied international bans, boycotts and sanctions to press ahead with an offensive it says is aimed at defending Ukraine's Russian speakers and toppling the leadership.

Germany has already promised arms for Ukraine, while the EU said, in a first, that it will buy and supply arms to the country.

But fears are growing of an all-out assault to capture Kyiv, a city of 2.8 million.

Satellite images provided by US firm Mazar showed a 40-mile build-up of Russian armored vehicles and artillery north of the capital.

Inside Kyiv, makeshift barricades dotted the streets and residents lined up outside the few shops open to buy essentials.

Russia's invasion has triggered a widening international sporting ban and Western nations have moved to further isolate Russia, responding with an intensifying diplomatic, economic and cultural backlash.

Apple on Tuesday stopped all sales in Russia. And the European Union banned Russian state media outlets RT and Sputnik from broadcasting in the bloc while also barring some Russian banks from the SWIFT bank system.

burs-ft/ec