Pakistani police have stepped up their operations at a mosque in Islamabad, on the fifth day of confrontation with radical Islamists barricaded there.

Heavy bursts of gunfire and explosions rocked the Red Mosque overnight after armoured vehicles moved in.

Police seized control of a seminary in the capital run by clerics from the mosque, arresting dozens of students.
Several hundred people, including children, have been holding out against the authorities since Tuesday. Water and power to the mosque have been cut off and food is said to be getting scarce.
Heavy exchanges of fire erupted at the complex early on Saturday. The two explosions overnight were the biggest so far in the siege and were heard as far as 8km (5 miles) away. Big chunks of debris, believed to be part of the mosque's perimeter wall, were blown high above the surrounding treetops.

On Friday an attempt by a group of students to break out sparked a co-ordinated assault on three sides by armoured personnel carriers and rangers. Two students were killed and at least 10 wounded, four of them seriously.

At least 19 people have been killed since the start of the stand-off. The mosque's deputy leader, Abdul Rashid Ghazi, said he and his followers are willing to lay down their guns but would rather die than surrender.