Dressed in the blue and yellow of Ukraine's flag and bearing posters like "No World War 3" and "Russians go home", hundreds of thousands of people took to the streets worldwide Sunday denouncing Russia's invasion of its neighbour.

From Berlin to Baghdad, from Washington to Saint Petersburg, demonstrators chanted "shame" against Russian President Vladimir Putin while others waved banners with slogans like "Putin murderer" or "stop the monster".

In the German capital, police estimated turnout to be at least 100,000, while Prague drew 70,000 and Amsterdam 15,000.

Organisers of the Berlin protest put the numbers at five times the police estimate, with demonstrators massing at the Brandenburg Gate, a stone's throw away from the imposing Russian embassy.

Although the embassy -- in which Russian diplomats both work and live -- was cordoned off by police, some protesters gathered in front shouting "glory to Ukraine" and singing Ukrainian songs.

"It is important to me for Germany to show that it is standing for democracy in Europe," said Hans Georg Kieler, 49, who was at the demonstration.

He praised Germany's decision to begin delivering armaments to Ukraine, but said "we could have helped Ukraine more".

Ukrainian Valeria Moiseeva was also at the march.

"I hate Russia, I hate all Russians," the pregnant 35-year-old said, adding that her mother was now sitting in a cellar in Kyiv in fear of bombs.

'Madman'

In Russia's second city of Saint Petersburg, around 400 people gathered in defiance of strict protest laws, holding posters reading "No to war", "Russians go home" and "Peace to Ukraine".

More than 2,000 people were detained in demonstrations across the country Sunday, following thousands of arrests this week, but protesters remained undeterred.

"It is a shame that there are hundreds, maybe thousands, of us and not millions," 35-year-old engineer Vladimir Vilokhonov told AFP in Saint Petersburg.

In the US capital, a few thousand people waved Ukrainian and American flags in front of the White House as they urged President Joe Biden to do more to halt Putin's aggression.

"Something needs to be done, we can't just sit by and have another World War Two or another Hitler take control," said Diana Vasylkevych, a 24-year-old student wrapped in a Ukrainian flag.

"So we're here today to just try to make a difference," she said, adding she has spoken to relatives back home who have been hiding in bomb shelters. "It's horrendous".

Americans nationwide came out to denounce Putin and express support for Ukraine, from San Francisco to Detroit, Chicago and Kansas City. Thousands also demonstrated in the Canadian city of Toronto.

Several thousand people gathered in Rome's city centre, answering a call from Italy's 235,000-strong Ukrainian community to rally.

"We are strong but we are alone now. One small country cannot protect the whole world from one bad person" Yvanna Bovik said.

In Prague, tens of thousands gathered at the central Wenceslas Square, including Roman Novotny, who travelled around 300 kilometres (186 miles) from Uherske Hradiste in the country's southeast.

"We all have to do our best," he told AFP, carrying a banner slamming Putin. "It's a difficult situation because the madman has nuclear weapons. I think he has cut himself off from the entire world, totally."

Meanwhile in Lithuania, Belarusian opposition leader Svetlana Tikhanovskaya led hundreds of her countrymen in protest against the Minsk regime for allowing Putin's army to use the country as a launchpad into Ukraine.

Chanting "Long live Belarus" and "Glory to Ukraine", they said they wanted the world to understand that ordinary Belarusians oppose the attack on Ukraine.

"Our Ukrainian brothers would not forgive us for our silence," Tikhanovskaya, who lives in exile in Lithuania, told reporters.

Voicing shame at Belarus strongman Alexander Lukashenko's actions, Sergei Bigel, a 39-year-old transport worker, told AFP: "This is a disgrace to the whole world. It is like stabbing a friend in the back."

A women's protest also massed near the Russian embassy in Vilnius, with people holding banners like "Putin = killer" and "See you in hell", while others brought wreaths.

Ruta Januliene, 37, called the Ukraine war "pointless" and said she was concerned for "the future and safety of children" there.

"It is hard for me to speak, it hurts a lot. I would like Putin to shoot himself and end all of this," she said, sobbing.

In Denmark, Prime Minister Mette Frederiksen joined 10,000 people in front of the Russian embassy in Copenhagen to condemn the invasion.

"It is all of you and all of Europe who are threatened by Russia", she told the crowd.

"We cry with you", she said, addressing Ukrainians.