At least 13 people have been injured in an explosion in the capital of Indonesia's troubled Aceh province, on the country's independence day.

Two children were among the injured

The home-made device was thrown into a crowd gathering to celebrate the occasion, but it did not disrupt the ceremony, police said.

No group has admitted carrying out the attack, which comes two days before the Indonesian Government is to unveil its plans on dealing with the separatist Free Aceh Movement (Gam). Gam called for a general strike on Saturday.

Indonesia is marking the 57th anniversary of independence from Dutch colonial rule.

Minor injuries

Eyewitnesses in Aceh say the atmosphere in the run-up to the day has been one of fear.

The BBC's Jakarta correspondent says it is usually a time of increased tension between the separatist rebels and security forces and this year has been no exception, with a series of explosions, shootings and demonstrations.

Two children were among those injured in Saturday's attack.

"The victims suffered minor injuries from the bomb and were taken to two nearby hospitals in the capital for treatment," state-run Antara news agency reported.

A witness said many of the wounded had left the hospital by late afternoon.

"It was a low level bomb and I'm sure our security measures were ample to guard the celebrations," police chief Yusuf Mangga Barani told reporters.

A number of similar attacks have been carried out by Gam activists in Banda Aceh, but the movement said it was not behind Saturday's bomb.

"Maybe the explosion... was carried out by people ordered by the security forces or it could also have been done by the security forces themselves," Gam's field commander Amri bin Abdul Wahab, said, quoted by AFP news agency.

Our correspondent says that, following the initial panic, some people returned to continue the Independence Day celebrations, but the mood has been very subdued, with most ordinary people who are not obliged to attend the official functions, staying at home.

New policy

Gam called for a halt to all business activities "unless really necessary" on Saturday.

The call appears to have had some impact, particularly in the town of Lhokseumawe, where the Exxon Mobil oil and gas facilities are based.

The strike call came ahead of a cabinet meeting on Monday, where the government in Jakarta is expected to announce a new policy for dealing with the troubled region.

President Megawati prefers to clamp down on the separatists

Correspondents say options under discussion include intensifying military operations against the separatists and the introduction of a civil or military state of emergency.

The announcement of the central government's new policy on Aceh was originally due at the beginning of August.

But it was delayed by a fortnight.

Both President Megawati Sukarnoputri and Security Minister Susilo Bambang Yudhoyono have hinted that a crackdown was imminent against guerrillas who have waged a 26-year battle for independence. But our correspondent says that appears to be highly unlikely.