YANGON (REUTERS) - Myanmar security forces fired at pro-democracy activists taking part in street demonstrations on Thursday (March 25), killing at least four people, news reports said, a day after a nationwide silent strike in protest against last month's military coup.

Four people were killed in the town of Taunggyi in central Myanmar in the shooting, the Myanmar Now news portal said.

Thousands of people held street protests in the commercial capital Yangon, the central city of Monywa and several other towns, according to witnesses and social media posts.

"Are we united? Yes we are," protesters shouted in Monywa. "The revolution must prevail."

Ms Nant Khi Phyu Aye, one of the those on the street, said many of the protesters were youngsters. "They want to protest every day without skipping one day," she told Reuters.

Police fired at a street demonstration in the city of Mawlamyine and arrested 20 people, the Hinthar Media Corp said. At least two people were injured, it said.

Other media outlets reported at least five people sustained bullet wounds when security forces opened fire on protests in other towns. Reuters could not independently verify the reports.

At least 286 people have been killed since the Feb 1 coup in the crackdown on protests, according to the Assistance Association for Political Prisoners (AAPP) activist group.

In a sign of growing international pressure, the United States and Britain imposed sanctions on two conglomerates controlled by Myanmar's military.

Wednesday's silent strike left normally bustling areas of commercial hubs like Yangon and Monywa virtually deserted.

While the scale of the protests had been dropping in recent days, activists had called for big demonstrations on Thursday.

"The strongest storm comes after the silence," protest leader Ei Thinzar Maung said in a social media post.

Candle-lit vigils took place across the country again overnight, photographs on social media showed.

In Thanlyin on the outskirts of Yangon, protesters held up placards reading: "We don't accept military coup", while medical staff wearing white coats held a dawn march in the second city of Mandalay.

Five more people were wounded overnight in Mandalay, Myanmar Now reported. A 16-year-old man died after being shot in the back, it said.

The funeral of a seven-year-old girl killed on Tuesday, the youngest known victim of the crackdown, took place on Wednesday in Mandalay.

A spokesman for the military, which said on Tuesday 164 protesters had been killed, did not answer calls seeking comment.

The junta on Wednesday freed hundreds of people arrested in its crackdown on protests against the overthrow of the elected government of Aung Sang Suu Kyi.

There was no word from authorities on how many prisoners were released, but AAPP said 628 were freed on Wednesday out of more than 2,900 arrested since the coup.

About 1,000 people had been freed in all, it said. Among those released was Polish photojournalist Robert Bociaga, who was arrested in Taunggyi two weeks ago.

He said in a message that he was leaving Myanmar on Thursday.

Singapore foreign minister in Jakarta

The junta has faced international condemnation for the coup that halted Myanmar's slow transition to democracy and for its deadly suppression of dissent.

It has tried to justify the takeover by saying a Nov 8 election won by Ms Suu Kyi's National League for Democracy (NLD) was fraudulent - an accusation the electoral commission has rejected.

Military leaders have promised a new election but have not set a date and have declared a state of emergency.

Suu Kyi, who won the Nobel Peace Prize in 1991 for her campaign to bring democratic civilian rule to Myanmar, has been in detention since the coup and faces charges that her lawyer says have been cooked up to discredit her.

The European Union and the US imposed sanctions on Monday against individuals involved in the coup and the repression of the demonstrators.

The European Union and the United States imposed sanctions on Monday against individuals involved in the coup and the repression of the demonstrators.

Singapore's Foreign Minister Vivian Balakrishnan met his Indonesian counterpart in Jakarta on Thursday and both leaders backed convening a summit of Asean leaders on Myanmar, saying the region should reach a common standing on the crisis.