At least 13 people including two policewomen were injured when an angry crowd threw stones at the trial of a popular pro-independence activist in Indonesia's Papua province, officials said.

Hundreds of supporters of Philip Karmas blocked the main entrance gate to the district court buildings near the Papua capital of Jayapura and began pelting the estimated 300 police inside with rocks.

"They were angered because Philip Karmas, unlike in past hearings, was not allowed to address the crowd of supporters after the trial [hearing]," Judge Ichsan, who heard the case, told AFP.

Karmas, who is being tried for hoisting the outlawed Papua separatist flag, had always been allowed to address his supporters either before or after hearings, Ichsan said.

"This time the defendant was directly put into the vehicle... to be immediately taken back to his detention cell," he said. "The mob grew angry and first closed the main gate and then began pelting stones at whoever was inside." Police fired warning shots into the air to disperse the riot, Abepura police Master Sergeant Suyitno told AFP.

A court official who declined to be named said she had seen at least two policewomen and a civilian man bleeding from head injuries.

A nurse at the emergency ward of Jayapura's general hospital said 11 civilians were admitted, none of them with gunshot wounds. The police hospital, where the wounded officers were taken for treatment, declined to comment.

Shops in the suburb of Abepura remained closed after the crowd was dispersed at about 1pm, with some onlookers staying outside the court building.

Karmas and three of his supporters are on trial for hoisting the flag on December 1, 2004. Prosecutors have recommended the judge sentence them each to five years in jail.

Papua has been the scene of a sporadic guerrilla rebellion since 1963 when Indonesia took over the mountainous and undeveloped territory formerly known as Irian Jaya from Dutch colonisers. There have been widespread allegations of military abuses.