Military officials in Burma have used tear gas to disperse hundreds of monks holding a rally in the north-west city of Sittwe, reports from the area say.
Unlike in Sittwe, the protest in Rangoon remained peaceful
Some of them were beaten and several were arrested, eyewitnesses say.
Large numbers of monks have also held protests in at least five other towns and cities across the country, including the former capital Rangoon.
They are demanding a government apology for the violent break-up of a recent rally against a sudden fuel price rise.
A new group that draws on militant youth elements in the clergy, the Alliance of All Burmese Buddhist Monks, appears to be co-ordinating the monks' protests.
It has asked its followers across the country to refuse alms and offerings from anyone connected to the military.
The monks' actions are deeply embarrassing to Burma's military rulers but present them with a difficult dilemma, according to the BBC's South East Asia correspondent Jonathan Head.
Monks are highly respected figures in Burmese society, and treating protesting monks in the same way they might treat dissidents and ordinary citizens risks provoking huge public anger, he adds.
The monks had given the government a deadline of Monday night to apologise for its actions during an earlier rally in the city of Pakokku, when soldiers and state-backed militia reportedly beat up several monks.
The deadline passed with no apology, so a series of protests were planned on Tuesday in Rangoon and other locations.
The rally in Rangoon was largely peaceful, although there were reports of military officials preventing monks from gaining access to the city's famed Shwedagon Pagoda.
But reports from the city of Sittwe indicate that the authorities there fired tear gas to break up a protest of about 1,000 monks and civilian demonstrators.
Three or four monks were arrested, and members of the crowd were hit and slapped, a witness told Reuters news agency.
Fuel price hike
The monks' demonstrations are the latest in a series of recent protests in Burma, originally sparked by the military junta's decision to double the price of petrol and diesel on 15 August.
The move was not announced ahead of time and the reasons behind it remain unclear, but it has hit people hard.
Demonstrations have continued despite the arrest of many of Burma's most prominent activists.
The protests are likely to put added heat on the government, which is already under intense international pressure to implement democratic change.
Monks have been at the forefront of protests against the government in the past.
A spokesman for the Alliance of All Burmese Buddhist Monks told the BBC that the monks had learnt from their experiences in 1988 and 1990 when their protests were easily put down by the military.
This time, he said, their leaders would remain underground.