Updated

A mob opposed to public discussion of Indonesia's 1965 massacre of communists tried to force its way into a Jakarta building where they believed communists were meeting, injuring five policemen.

Jakarta police spokesman Argo Yuwono said 22 people were arrested early Monday for rioting and five officers were injured in the confrontation.

The melee came a day after police blockaded the building on Saturday to stop a public forum on the massacre, in which historians say half a million people were killed, from going ahead.

Bonnie Setiawan, an organizer of the forum, said about 200 people were trapped in the building, which is home to a legal aid institute, for hours on Sunday night while more than 1,000 people protested outside.

The protesters shouted that the people inside were members of the long-outlawed Indonesian Communist Party and threw rocks, breaking windows, he said.

Indonesia held a ground-breaking symposium on the massacre last year, breaking a half century of near silence on the issue, but the military, Islamic groups and senior figures in the government are opposed to unearthing the truth, saying it could revive communism.

The Indonesian Communist Party was the third largest in the world with an estimated 3 million members when an unsuccessful coup by pro-communist military officers in 1965 triggered a monthslong bloodletting by the army and Islamic groups that engulfed the country and ushered in the Suharto dictatorship.

Yuwono said police blockaded the forum on Saturday because organizers hadn't requested permission for it.

Setiawan said police had violated the constitutional rights to freedom of association and assembly. The meeting on Sunday was intended as a discussion of challenges to democracy in Indonesia, he said.