Banda Aceh – At least 30 bombs or grenade blasts were heard around the main city in the restive province of Aceh in the run-up to Indonesia's Independence Day Friday, residents said.

The blasts cut power to the provincial capital Banda Aceh for some hours Thursday night and badly damaged four banks, an AFP reporter saw. One was burnt to the ground.

Flag-raising ceremonies went ahead in the province on Sumatra island where a separatist revolt has been waged since the mid-1970s. But witnesses said Banda Aceh remained tense, with streets very quiet, most shops closed and a transport strike still in force.

Residents said at least 30 blasts were heard Thursday evening up to midnight and two more on Friday morning in and around Banda Aceh. Four banks on the campus of Syiah Kuala University in the nearby Darussalam area were bombed Thursday evening and Bank BNI was burnt to the ground. There was no immediate information on casualties or the target of most of the bombs.

Aceh military spokesman Colonel Firdaus reported three blasts between Thursday evening and Friday morning around Lhokseumawe, 200 kilometres east of Banda Aceh.

A suspected member of the Free Aceh Movement (GAM) lost a hand when he tried to throw a grenade at a police convoy at Tempok Tengah Thursday night, Firdaus said. The man was in custody in hospital and no one else was hurt.

At Pusong Baru early Friday a small boy was injured when a home-made bomb went off in a badminton court. Firdaus blamed rebels for the blast. He said another home-made bomb went off at a small reservoir at Blang Panjang. No one was hurt but the reservoir was slightly damaged, the military spokesman said.

Apart from civil servants obliged to attend flag-raising ceremonies, most people stayed indoors. Main towns displayed a sea of red and white national flags but some residents said they flew them to avoid reprisals from the military.

"If we don't raise the flag there will be people coming to our houses to threaten us," one spice seller told AFP. Asked who, he replied: "The authorities. It's better to raise the flag than face unwanted things happening to you." A sharpshooter was posted on a rooftop as the flag raising ceremony went ahead in Lhokseumawe and a police armoured car patrolled the streets. Fewer than 50 residents watched.

Firdaus also said troops are unearthing a suspected mass grave in the Lhoong area of West Aceh following a tip-off from a GAM official who turned himself in on August 4. He said the ex-rebel, identified as Teungku Amransyah, told authorities of a grave containing the bodies of 48 civilians allegedly killed by GAM. Troops Thursday uncovered nine bodies from the site and work was continuing, he said.

Bus operators in Aceh have been ordered to halt operations or risk having their vehicles torched. Dozens of schools throughout the province have been set ablaze. The military has blamed rebels, saying they aim to prevent Independence Day celebrations in schools.

GAM has waged a guerrilla war for 25 years in its campaign for an independent Islamic state in the fervently Muslim region. More than 1,100 people, mostly civilians, have died this year alone.