ALGIERS — A bomb ripped through an open-air market outside the capital on Algeria's independence day Friday, killing at least 30 people and wounding 36 others, the official APS news agency reported.

The bomb was hidden in the mouth of a sewer at a market bustling with morning shoppers in Larba, about 25 kilometres southeast of the capital, APS said, quoting a statement from military authorities in the Algiers area.

The agency originally reported 29 dead, but a wounded person later died. It could not be immediately determined whether the attack, the deadliest this year, was the work of Islamic extremists. Radical Muslims have led a 10-year insurgency to try to topple the North African country's military-backed government.

The attack came as Algerians celebrated the 40th year of their independence from France, won after a brutal seven-year war. Security had been tightened around the capital ahead of independence day.

Witnesses reported a second explosion at a Mediterranean beach known as Azur Plage, some 30 kilometres west of the capital. The blast caused panic but no injuries, they said.

An estimated 120,000 people have been killed since the violence started in 1992 after the army aborted legislative elections to thwart victory by a Muslim fundamentalist party.

The Larba area was long a haunt of the radical Armed Islamic Group, or GIA, blamed for most civilian massacres.

Security forces were thought to have largely cleaned out the area around Algiers and the area to the south, the Mitidja Plain, part of which was once controlled by extremists.

However, violence has recently increased in Algeria, with assailants targeting public transport and isolated hamlets.

The GIA and another movement, the Salafist Group for Preaching and Call, refused an amnesty plan offered by President Abdelaziz Bouteflika to bring peace to the tormented country.

The groups are on Washington's list of terrorist organizations. U.S. officials have praised Algeria for its efforts in fighting terrorism.

Numerous suspected Algerian Islamic extremists, or those of Algerian origin, have been implicated in recent plots to attack targets in Europe and elsewhere. Since Sept. 11, dozens have been detained for alleged connections to Osama bin Laden's al-Qaida network.

In the past month, 25 people were killed in three separate attacks on buses, one not far from Larba.

More than 750 people have been killed since the start of the year in Algeria, according to an unofficial account by the press.