People carry an injured man at a local hospital following the attack at Quetta mosque

Additional reporting by Asif Farooqi, IOL Pakistan Correspondent

ISLAMABAD, July 4 (IslamOnline.net & News Agencies) – At least 31 people were killed and 50 injured in a suspected "suicide" attack at the main Shiite mosque in the southwestern Pakistani city of Quetta Friday, July 4, officials said.

"At least 31 people were killed and another 50 were wounded in the attack," head of the interior ministry's National Crises Management Cell Brigadier Javed Cheema told Agence France-Presse (AFP).

Armed policemen and paramilitary troops spread across the city and a curfew was imposed following the deadly attack.

"Curfew has been clamped down in Quetta and paramilitary and police have been deployed to control the rioting," Cheema said.

Asked if the security forces had been given orders to shoot rioters on sight, he said it was "normal procedure in a curfew situation".

Police said four “suicide killers” attacked the main Shiite mosque with hand grenades and automatic rifles minutes before the Friday prayers.

 Police said the exact number of attackers was still unclear, adding that one of them was blown up inside the mosque by a grenade and another was killed at the main entrance by mosque guards.

A third suspected attacker wounded in firing died later in hospital, AFP quoted a police officer as saying.

Police said the attack was part of a spree of sectarian killings which has gripped Pakistan for many years now.

Hundreds of people have been killed in attack on Shiite and Sunni mosques over the past years.

The Mosque which saw the attack Friday belong to the Shiite Hazar tribe.

Soon after the killings, Hazar tribesmen and Shiite community took to the streets to protest the killings.

The protests turned violent when the protesters, some of them armed, set on fire a portion of the hospital where the dead and injured were taken.

They also smashed and burnt nearby shops and cars plying the main Quetta roads.

Provincial chief of Police Shoaib Suddle told reporters in Quetta that the attack was related to the sectarian violence.

He said it is too early to predict as to who could be behind this attack but said it appeared to be a sectarian attack.

This was second attack against Hazar Shiite in Quetta in less than a month.

Several people were injured when grenades were hurled on a mosque in Quetta suburb last month.

Suddle said the attackers were apparently on a suicide mission as they blew grenades in their hands while some of them were thrown on the worshippers.

To keep the situation under control, the police chief said the district government called in the army and imposed indefinite curfew.

The situation was reportedly calming down while army patrols announced the curfew on loudspeakers and ordered people to stay inside their houses.

"Vested Interests"

The suspected sectarian attack came as Pakistan President Pervez Musharraf was briefing newsmen in Paris at the end of his four-nation tour aimed at wooing foreign investors.

Musharraf said there were "some elements in Pakistan that undermine whatever the vast majority stands for.

"We have to act very strongly against them," he said, noting that the government was aware of what he described as "vested interests" working against the authorities in Islamabad.

"There will be no dearth of strength and resolve in acting against them," Musharraf said.

Sectarian killings mainly carried out by outlawed militant groups with political motives to destabilize the government, have targeted both Sunnis and Shiites.

In the southern port city of Karachi in February, nine Shiites were killed outside a mosque by gunmen on motorcycles. Days later, two Shiites were shot dead.

Less than a month ago, 11 police recruits were killed and nine wounded when gunmen opened fire on their vehicle in Quetta.

Police deemed the incident a sectarian attack, because the men were all from the Shiite Hazara tribe.

Shiites form about 20 percent of Pakistan's Sunni-dominated 145 million population.

While sectarian violence appears to be on the increase, attacks on Western and Christian targets have slowed since 2002.

They were blamed on militants irked by Musharraf's decision to back the U.S. war on neighboring Afghanistan.