Explosions heard from Pakistani mosque

ISLAMABAD (Reuters) - Loud explosions were heard on Thursday from the vicinity of a radical Pakistani mosque being besieged by security forces but the cause was not immediately clear, witnesses said.

About eight explosions were followed by some gunfire but it was not clear if security forces had launched an assault on the Lal Masjid, or Red Mosque, where hardline religious students are defying a government order to surrender.

The explosions were followed by an announcement broadcast from security force loudspeakers outside the mosque, calling on the students to surrender, a witness said.

"All people in the mosque should surrender or they will be responsible for losses," the witness who lives in the neighborhood cited security forces as saying in the announcement.

Sixteen people have been killed in violence that erupted at the mosque on Tuesday after a months-long stand-off between the authorities and a Taliban-style movement based there.

A senior police official said "activity" in the area had intensified and security forces were taking "necessary action". He did not elaborate.

Hundreds of police and soldiers, backed by armored personnel carriers and with orders to shoot armed resisters on sight, sealed off the mosque and imposed an indefinite curfew in the neighborhood after Tuesday's clashes.