Almost 50 people were injured in the eastern Indonesian city of Ambon in the worst outbreak of violence since a Muslim-Christian peace agreement in February.

Trouble began with a bombing in the city, which prompted angry crowds from both faiths to gather at the governor's office. The office was set ablaze, stones were thrown and police and troops fired warning shots to disperse the crowd. Security forces contained the two groups in separate areas as firefighters tackled the blaze. It was not clear which side started the fire.

At least 37 people were rushed to the general hospital in Ambon, a doctor who identified herself as Conny said. She could not give details of their condition. Nine others were admitted to a private hospital and four of them were seriously hurt, a nurse told AFP. She could not say whether they were injured in the blast or in efforts to disperse the crowd.

The explosion was initially said to be a car bomb. But some witnesses said a bomb was thrown from a speeding van near the governor's office.

C.J. Bohm, a Catholic priest at the Crisis Center Diocese of Ambon, said he suspected that the mob who set fire to the governor's office were Christians. "I think it is quite visible because it is a Christian area," he said. He described the explosion as powerful but said he had not received information on casualties.

The city and the rest of the Maluku islands had been relatively peaceful since Muslim and Christian representatives reached a government-sponsored peace accord in February to end three years of sectarian fighting. The violence left more than 5,000 people killed and more than half a million homeless.