Pakistan's minority Shiite Muslims marked the key holy day of Ashura with processions Monday, as the death toll from a homicide bombing at a Shiite gathering in the capital of Pakistan-controlled Kashmir increased to eight, police said.

Another 80 people were wounded in Sunday night's bombing in Muzaffarabad — a rare sectarian attack in an area police say has little history of militant violence. The dead included three police officers, said police official Yasin Baig, adding that another 10 police were among the wounded.

The homicide bomber set off explosives he was carrying as police searched him outside a ceremony commemorating the seventh-century death of the Prophet Muhammad's grandson during the Islamic holy month of Muharram.

Security has been tightened across Pakistan during Muharram, and particularly for Monday's Ashura, the 10th day of Muharram, a month of mourning often marred by bombings and fighting between Pakistan's Sunni Muslim majority and its Shiite minority.

In the northwestern city of Peshawar, which has been repeatedly hit by suicide bombings in the past months, thousands of police were guarding processions, and troops were on standby, local police chief Liaqat Ali Khan said.

"Our security level is red alert," Khan said, adding that the recent wave of attacks required police to be extra vigilant.

More than 500 people have been killed in attacks across Pakistan since October. Insurgents are suspected of avenging a U.S.-supported Pakistani army offensive against the Taliban in a northwest tribal region along the Afghan border.

Maj. Aurangzeb Khan said paramilitary forces were deployed and were carrying out helicopter patrols in the southern port city of Karachi, where a blast that authorities attributed to a buildup of gas in a sewage pipe wounded about 30 people on Sunday.

"Our men will remain with all the processions till their culmination," Khan said.

In the eastern city of Lahore, all entry and exit points to processions were blocked to traffic and anyone joining a procession had to pass through scanners, said police official Chaudhry Shafiq.

"There is always a threat, especially in the ongoing terror attacks," Shafiq said.

After Sunday night's bombing in Kashmir's Muzaffarabad, Baig, the police official there, said Shiite mourners at the commemoration ceremony took to the streets to protest the bombing, with some firing shots in the air. Baig said authorities restored order within about an hour.

He said it was the first time a suicide bomber attacked a Shiite gathering in the region.

Muslim militants have fought for decades to free Kashmir, which is split between India and Pakistan and claimed by both, from New Delhi's rule. But while Pakistani Kashmir has served as a base for anti-India insurgents to train and launch attacks, the region has largely been spared violence, with militants focusing on the Indian-controlled portion.

Many of the region's armed groups were started with support from Islamabad. But some of them have turned against their former patrons and joined forces with the Taliban because the government has reduced its support under U.S. pressure.

The partnership is a dangerous development for Pakistan as it could enable the Taliban to carry out attacks more easily outside its sanctuary in the country's tribal areas in the northwest. More than 500 people have been killed in retaliatory attacks since the military launched a major anti-Taliban offensive in mid-October in the militant stronghold of South Waziristan near the Afghan border.

In the latest South Waziristan fighting, the army said Monday that militants attempted to raid an army post Sunday night, leading to a clash which left 15 militants and two soldiers dead, and another three soldiers wounded.