YANGON (AFP) - Riot police sealed hundreds of Myanmar student protesters inside a monastery on Monday in a tense standoff, activists said, blocking their planned march to Yangon to call for education reforms.

Scores of security personnel encircled the monastery in Letpadan town, some 130 kilometres north of Myanmar's main city Yangon, trapping around 300 students inside since early morning.

Authorities appear increasingly uneasy over the months-long rallies by different student organisations, which have persisted in some areas despite parliamentary efforts to rethink a controversial education bill.

"Our students are inside the monastery and all the exits and entrances have been closed. The tension has grown since this morning," said one activist, also trapped inside the Aung Myae Baikman monastery, who spoke on condition of anonymity.

The group, which began marching from Mandalay in January, has been camped at the monastery since pausing its rally last week after negotiations with the government.

The talks saw officials pledge a number of changes to the education bill, currently being reviewed by parliament after it was passed as law late last year, but the protesters indicated Sunday the march would resume.

They say the bill is undemocratic and are calling for changes including decentralising the education system, enabling students to form unions and teaching in ethnic minority languages.

Student activism is a potent political force in Myanmar with young campaigners at the forefront of several major uprisings, including a mass 1988 demonstration that ended in a bloody military assault on protesters.

The government has appeared anxious to prevent the marchers from reaching Yangon, warning activists against travelling to the city.

The student rallies, which initially began in November before flaring again this year, have so far taken place without permission in the country, where illegal protests are often met with arrests.

Activists on Monday said authorities had told them to seek approval from the home affairs ministry to continue the demonstration, although they were yet to do so.

The activist inside Aung Myae Baikman monastery added that the students planned to march to the next large town before driving to Yangon, "hoisting the students' flags and singing songs" before meeting outside the revered Shwedagon pagoda.