Tomi Soetjipto, Jakarta – A bomb blast ripped through the ground floor of a busy shopping centre in the Indonesian capital Jakarta on Wednesday evening, injuring at least five people, police and witnesses said.

The explosion hit the shopping complex in the central Senen district at around 8pm as commuters were making last-minute purchases before heading home, blowing out windows and sending clouds of thick smoke into the air.

"This bomb is a terrorist act. It's aim is pretty clear, it is to create excessive fear among society," Jakarta governor Sutiyoso told reporters, adding that no one had been killed. "This is not a stand-alone action, it is part of a syndicated act." It was unclear who was behind the attack, he said.

There have been several unsolved bomb attacks in Indonesia in recent months amid political tension that climaxed in the ousting of the country's first democratically-elected leader, Abdurrahman Wahid, by the top legislature last week.

Thick smoke covered the multi-storey shopping complex after Wednesday's blast, which was heard 1.5 km away.

Hundreds of bystanders milled about as ambulances rushed the injured to hospital. Police said one person had been hurt seriously but gave no details. "There was one big explosion that was very loud. A pile of smoke came from the area," said Anisya, who runs a fried chicken stall across from the mall. "It was like a tremor," she told Reuters.

Police closed the shopping centre and evacuated the building. The bomb squad also arrived not long after the blast.

Indonesia has been battered by violence and political instability since former President Suharto stepped down in disgrace more than three years ago. Indonesians hope the appointment of new President Megawati Sukarnoputri last week will finally usher in some stability.