US President Joe Biden is monitoring unrest in China by protesters demanding an end to Covid lockdowns and greater political freedoms, the White House said Monday, as smaller rallies popped up in the United States.

The comments came after hundreds of people took to the streets in China's major cities over the weekend, in a rare outpouring of public frustration that has spread to international Chinese-speaking communities.

"He's monitoring this. We all are," National Security Council spokesman John Kirby told reporters Monday.

Kirby would not describe Biden's reaction to the demonstrators' demands, saying: "The president's not going to speak for protesters around the world. They're speaking for themselves."

But he stressed the US support for the demonstrators' rights.

"People should be allowed the right to assemble and to peacefully protest policies or laws or dictates that that they take issue with," Kirby said.

Earlier Monday, the State Department suggested that the United States viewed Beijing's Covid lockdown policies as excessive.

Discontent has been brewing for months in China over its harsh coronavirus control measures, with relentless testing, localized lockdowns and travel restrictions pushing many to the brink.

Around the United States, Chinese-speaking communities came together in vigils to mark lives lost to zero-Covid -- with the latest gatherings sparked by a deadly fire in Urumqi city.

- 'Solidarity' -

Around 100 people, many of them students, gathered in Washington Monday to call for greater freedoms and mourn those who died when a blaze tore through a building in northwestern Xinjiang's capital Urumqi last week.

Officials said 10 people were killed, and many blamed Covid lockdowns in the city for hampering rescue efforts.

"(Officials) are borrowing the pretext of Covid, but using excessively strict lockdowns to control China's population. They disregarded human lives," said a Chinese student surnamed Chen.

"I came here to grieve," the 21-year-old added.

Referring to protests across China, another student Zhou, 22, said: "My friends and I never imagined things would develop so rapidly."

Attendees held white sheets of paper symbolizing censorship and chanted slogans including "Freedom of speech! Freedom of assembly! Tear down the firewall!"

Members of the Uyghur community were also present, expressing anger over the casualties.

"The fire that caused the deaths awakened us," said Tahir Imin, an activist and academic.

A similar gathering took place on the US west coast as well.

In Los Angeles, over 100 people gathered outside the Chinese Consulate General on Sunday night with candles and fresh flowers, attendees told AFP.

"The atmosphere was mostly filled with anger, sadness and a little frustration, in solidarity with protesters in mainland China," said Michael Luo, a 25-year-old graduate student.

He described the event as peaceful, and a "leaderless movement."

In Washington, around 25 members of the Uyghur community gathered Monday outside the State Department as well, to call on the US and other democracies to apply further pressure on Beijing.

"We want them to issue a formal statement condemning the loss of lives, Uyghur lives, and to call for full transparency on the real number of deaths that occurred," said Salih Hudayar, a Uyghur-American who campaigns for Xinjiang independence.

"We're hoping that the international community supports these protesters in demanding accountability from the Chinese government," he added of protests in China.