Russia said Thursday that its military had achieved its goals set out for the first day of its invasion of Ukraine, after launching the attack despite warnings of sweeping Western sanctions.

"All of the tasks assigned to the groups of troops of the Armed Forces of the Russian Federation for the day were successfully completed," Defence Ministry spokesman Igor Konashenkov said.

Russian President Vladimir Putin launched a full-scale invasion of Ukraine on Thursday, unleashing air strikes and ordering ground troops across the border in fighting that Ukrainian authorities said left dozens of people dead.

The attack triggered Western warnings of unprecedented sanctions against Russia as NATO, EU and G7 leaders condemned the invasion and vowed to hold Moscow accountable.

Weeks of intense diplomacy failed to deter Putin, who massed over 150,000 troops on Ukraine's borders in what the West said was the biggest military build-up in Europe since World War II.

"I have decided to proceed with a special military operation," Putin said in a televised address before dawn on Thursday.

Shortly afterwards, the first bombardments were heard in Ukraine's capital, Kyiv, and several other cities, according to AFP correspondents.

Russian air strikes hit military installations across the country as ground forces moved in from the north, south and east, forcing many Ukrainians to flee their homes to the sounds of bombing.

Battle for airbase 

Across the country, at least 68 people were killed, including both soldiers and civilians, according to an AFP tally from Ukrainian official sources.

Air raid sirens sounded over Kyiv at the break of dawn after the city's main airport was hit in the first bombing of the city since World War II.

"I woke up because of the sounds of the bombing. I packed a bag and tried to escape," Maria Kashkoska told AFP, as she sheltered inside a metro station.

Ukraine said that Russian forces had managed to reach the region around Kyiv and a battle was underway for an airbase near the city.

An AFP reporter in the northern part of the city saw several low-flying helicopters overhead.

In the deadliest single strike reported by authorities, 18 people were killed at a military base near Ukraine's Black Sea port city of Odesa.

Ukraine's emergency services also said a military plane with 14 people on board crashed south of Kyiv and that it was determining how many people died.

Ukrainian President Volodymyr Zelensky declared martial law and accused Russia of acting like "Nazi Germany" but asked people not to panic and promised victory.

Ukrainian forces said they had killed "around 50 Russian occupiers" while repulsing an attack on a town on the frontline with Moscow-backed rebels, a toll that could not be immediately confirmed by AFP.

Feel sorry for everyone

In the eastern Ukrainian town of Chuguiv, a son wept over the body of his father among the wreckage of a missile strike in a residential district.

"I told him to leave," the man sobbed repeatedly, next to the twisted ruins of a car.

Elena Kurilo, a 52-year-old teacher was among 20 wounded recovering in hospital after a blast sent shards of glass from her windows into her face.

"Never, under any conditions will I submit Putin. It is better to die," she said.

On the Russian side of the border, in Pokrovskoye, there was a strange calm and no sign of the soldiers who had filled the village on Wednesday.

Anastasia Yashonkova came out of a store where she bought small toys and a lemonade for her four-year-old son. Holding her child by the hand, Yashonkova said all she wanted was peace.

"This is really scary," said the 30-year-old. "I feel sorry for everyone."

Panic on the markets 

Russia's defence ministry said it had destroyed over 70 military targets, including 11 airfields.

Ukraine said Russian tanks and heavy equipment crossed the border in several northern regions, in the east as well as from the Kremlin-annexed peninsula of Crimea in the south.

Kremlin spokesman Dmitry Peskov said the operation would last as long as necessary, saying there were "goals that need to be achieved".

"Ideally, Ukraine needs to be liberated and cleansed of Nazis," he told reporters, repeating unfounded claims made by the Kremlin about Ukraine's government.

The fighting roiled global financial markets, with stocks plunging and oil prices soaring past $100.

European wheat prices also hit a record high on expectations of lower supplies as Ukraine and Russia are two of the world's biggest producers.

Harshest sanctions

In his televised address, Putin justified the assault as a defence of the self-proclaimed Donetsk and Lugansk republics in eastern Ukraine.

The Kremlin earlier said the leaders of the two separatist territories had asked Moscow for military help against Kyiv after Putin recognised their independence on Monday.

A conflict between the separatists and government forces has dragged on since 2014, killing more than 14,000 people on both sides.

"Putin's aim is to end the existence of Ukraine as it was yesterday," said Tatyana Stanovaya, founder of the political consultancy R.Politik Center and a non-resident scholar at the Carnegie Moscow Center. 

"I cannot see anything that would stop Russia now".

US President Joe Biden spoke with Zelensky after the Russian assault began to vow US support.

He condemned the "unprovoked and unjustified attack," and vowed Russia would be held accountable.

Biden joined a virtual meeting of G7 leaders -- Britain, Canada, France, Germany, Italy, Japan and the United States -- on Thursday, likely to result in more sanctions against Russia.

In Brussels, EU foreign policy chief Josep Borrell said Russia would be hit with the "harshest sanctions" the European Union has ever imposed.

French President Emmanuel Macron said the events were a "turning point in the history of Europe".

NATO said it would hold a virtual summit and activate "defence plans" for allied countries.

But NATO chief Jens Stoltenberg said: "We don't have any plans to send NATO troops into Ukraine".

Russia has long demanded that Ukraine be forbidden from ever joining NATO and that US troops pull out from Eastern Europe. 

Putin this week set out a number of stringent conditions if the West wanted to de-escalate the crisis, saying Ukraine should drop its NATO ambition and become neutral.

The Russian invasion rattled eastern NATO members once dominated by Moscow, with several calling for a strong response from the military alliance.

Poland also said it would open nine reception centres along its border with Ukraine in anticipation of an influx of refugees.

In the Baltics, Lithuania declared a national and Latvia banned three Russian TV channels that were broadcasting in the country, saying they posted a "threat to national security".