Trouble erupted at rallies in the capital Islamabad and the eastern city of Lahore as Agha Ziauddin was being buried in the remote northern town of Gilgit, where he was ambushed in his car and fatally wounded last week.

The minority Shia leader died in a military hospital in Rawalpindi, near Islamabad, on Thursday, four days after he was brought there by helicopter from the Himalayan gateway town of Gilgit for treatment.

Gilgit and neighbouring Skardu have been under curfew and troops have been patrolling the streets since Saturday, when the attack on the cleric triggered an outbreak of sectarian violence in which 15 people were killed.

Some 200 people from the Imamia Student Organisation, the Shia youth wing, rallied in Islamabad, where police used teargas and batons to disperse them after they allegedly hurled rocks at officers, witnesses said.

Police rounded up dozens of students and took them away in police vans from the city center after the clash, they said.

Around 600 angry members of the same Shia group rallied outside the press club in Lahore, Pakistan's second largest city, where they were involved in a row with journalists after they blocked entry to the premises.

Witnesses said the demonstrators threw stones at the club building and also roughed up journalists, injuring five. They also destroyed media vehicles parked on the premises.

Police swooped on the protesters as they were leaving the area and took around 200 of them into custody, an AFP correspondent at the scene said.

The bodies of the Shia leader and his guard, who both died of their injuries in the same hospital on Thursday, were flown to Gilgit by helicopter for burial in his hometown.

Authorities have stepped up security across the country.

Sectarian bloodshed involving rival Sunni and Shia extremists has claimed more than 4,000 lives since late the 1980s. Shias form about 20 percent of Pakistan's 150 million population but are in a majority in Gilgit and Skardu.

Gilgit has a history of sectarian violence but the weekend disturbances were the worst since several people were killed in June last year.

"Authorities are preparing to bury the leader amid tight security," an AFP correspondent in Gilgit said. Despite rain about 1,500 people have reached the town's Shia mosque, according to residents.

Authorities have helped 36 foreigners -- 14 South Koreans, five Chinese, one Japanese and 16 Afghans -- to leave Gilgit, local officials said. Seventy Chinese engineers working on a hydroelectric project have also been moved.

Unrest erupted on Thursday after Ziauddin's death was announced, with mobs in Skardu torching a Sunni school and ransacking a Pakistan International Airlines office.

Investigators have said one of Ziauddin's alleged killers, who died in the shoot-out, belonged to a banned Sunni militant group.

Ziauddin served as prayer leader of the main Shia mosque in Gilgit for 15 years and was known as a moderate.