Soldiers respond to Aceh violence

Indonesian flags are everywhere in the Aceh capital

Hundreds of Indonesian troops are patrolling the streets of the capital of troubled northern Aceh province after more than 20 explosions there overnight.

The Free Aceh Movement says it carried out the blasts in Banda Aceh to coincide with Friday's official celebrations commemorating independence from Dutch colonial rule.

People rush to board buses before a transport strike

Four banks on the university campus and the capital's water supply are reported to have been attacked, as well as schools throughout the province. There are no reports of injuries.

On Thursday, Indonesian President Megawati Sukarnoputri apologised to the provinces of Aceh and Irian Jaya for human rights abuses committed by past governments.

We apologise to our brothers who have long suffered as a result of inappropriate national policies

President Megawati

But she said she would never allow them to break away from the Indonesian state, as East Timor did in 1999.

BBC South East Asia correspondent Jonathan Head says the bombing campaign overnight is a clear sign the rebels are not yet ready for reconciliation with central government.

Agency reports say the streets of Banda Aceh are quiet, and few buses are running after threats from the rebels.

The disturbances in Aceh came as security forces announced the discovery of a mass grave containing 48 bodies near Lhong village in the west of the province.

Mass grave

Aceh military spokesman Colonel Firdaus said they had been alerted to the mass grave by a Free Aceh official, who had turned himself in to the authorities.

If confirmed, this is the largest mass grave so far uncovered in Aceh, where some 6,000 people have died over the past decade in the separatist struggle.

The security forces launched an offensive against the rebels in March, since when more than 1,000 people have been killed.

Autonomy offer

In a speech on the eve of independence day, President Megawati urged the provinces to accept new autonomy packages which will give them a greater say in their own affairs.

In her first major address since being sworn in last month, Megawati said: "We apologise to our brothers who have long suffered as a result of inappropriate national policies.

President Megawati is calling for national unity

"We need to pay more attention to human rights.

"We need a security force which is effective, highly disciplined and under the control of the government."

She urged separatists to abandon their struggle and "help build a new Indonesia".

The situation in Aceh and Irian Jaya was completely different from East Timor, she said, adding that rebels should be aware that they did not have any support from foreign countries.

Although spokesmen for the separatist movements were quick to reject the proposals, Megawati has said she will travel to Aceh in early September to try to find a peaceful solution to the violence.