Burma's military government has stopped thousands of students from attending university as calls mounted for the release of Aung San Suu Kyi.
Aung San Suu Kyi has spent much of the last decade in detention
The opposition leader was taken into "protective custody" on Friday after clashes between members of her National League for Democracy (NLD) and government supporters left several people dead.
The BBC's Larry Jagan says university campuses, which have been closed indefinitely, have in the past been at the centre of political activity and the authorities are worried that students may organise protests.
Although Burma's media has reported nothing of the weekend's events, Burma rights campaigner Debbie Stothard told the BBC that word was slowly getting out and that "if the young people actually found out exactly what happened... it is very possible that there will be nationwide unrest".
The NLD leader is being held at a military guesthouse in the capital, Rangoon. NLD offices have been shut and one Burmese pro-democracy group said it had heard reports that up to 200 other NLD members had been arrested.
Phone lines are said to have been cut, and it is extremely difficult to independently verify what is now happening in Burma.
Students at the gates of the University of Foreign
Language in Rangoon told the Associated Press that they had been given no warning that their classes would be suspended.
"I am surprised and disappointed with the closure. I am
about to get my degree in another four months," one student said.
The scheduled reopening of the country's primary and high
schools has also been postponed by two weeks, a school teacher told AP.
The military said four people were killed and 50 injured in Friday's clashes in the town of Yaway Oo, about 560 kilometres (400 miles) from Rangoon.
But separate reports estimate that up to 70 people died, including several monks who had joined Aung San Suu Kyi's entourage, but were unconnected with the NLD.
6 May - Aung San Suu Kyi begins tour of North
24 May - 10 NLD members jailed
26May - NLD complains of government 'harassment'
30 May - Clashes between NLD and pro-government supporters leave several dead
1 June - Aung San Suu Kyi taken to Rangoon for 'protective custody'
Debbie Stothard, co-ordinator of regional advocacy at Altsean (The Alternative Asean Network on Burma), said the latest developments were the culmination of growing tensions between the military and the NLD.
"I think this is all part of a consistent plan and programme by the military regime to shut down the NLD and to prevent Aung San Suu Kyi for further travel out of Rangoon. She's just attracting too much support every time she travels out of Rangoon, and this is extremely threatening to the regime," she said.
The United Nations, Japan, Australia, Thailand, Britain, France and Sweden have all expressed their alarm over the development.
Australian Foreign Minister Alexander Downer said his government had summoned Burma's ambassador to explain her detention.
Razali Ismail, a UN special envoy who in October 2000 helped end a long deadlock between the two sides, will proceed with a planned visit to Burma on Friday despite the detention of Aung San Suu Kyi, an aide said Monday.
Despite hopes that her release from house arrest last year was a sign that the junta was ready for political reform, Aung San Suu Kyi recently attacked the military for the slow pace of change and their apparent reluctance to start political talks.
Last week, 10 members of the pro-democracy movement were sentenced to stiff jail terms for organising public protests and being involved in clandestine activities.
And Aung San Suu Kyi's month-long political tour of the north had become increasingly tense, with repeated clashes between NLD supporters and members of the junta-sponsored Union Solidarity Development Association.
The NLD won elections in 1990 by a landslide, but the military regime which has run the country since 1962 refused to hand over power.
Aung San Suu Kyi has spent much of the subsequent decade under house arrest.