ISLAMABAD, Pakistan -- Gunmen opened fire on a commuter van and a rickshaw in the southwestern city of Quetta on Saturday, killing at least 11 Shiite Muslims, according to police officials. It was the latest in a series of deadly sectarian attacks in the city in the past few days.
A banned Sunni extremist militant group, Lashkar-e-Jhangvi, claimed responsibility for the attack.
Quetta, the capital of Baluchistan Province, which borders Afghanistan and Iran, has a history of sectarian and nationalist violence. Sunni extremists in the region have repeatedly attacked minority Shiites, who are mostly members of the Hazara ethnic group.
The latest spate of sectarian violence began with the killing of a Sunni scholar in Quetta on Thursday. Since then, Sunni militants have carried out several attacks on Shiites.
On Friday, gunmen attacked a bus carrying Shiite pilgrims, killing seven.
The police began rounding up members of the Sunni militant group and other suspects on Friday. On Saturday, Rao Amin Hashim, the inspector general of the provincial police, said that they had arrested 250 people and were conducting raids to detain more suspects.
In the attack on Saturday, two gunmen in a car sprayed a morning commuter van with bullets as it headed toward a marketplace from Hazara Town, a Hazara enclave in Quetta, the police said.
Nine men and a woman in the van were killed. Three people were seriously wounded.
A passing rickshaw also came under fire. The rickshaw's Shiite driver was killed, and two passengers were seriously wounded.
The attack set off a wave of violent protest, and angry Shiite demonstrators clashed with police officers in several parts of the city. Protesters blocked roads, burned tires and set two vehicles on fire outside the Bolan Medical Complex, where the wounded were taken for treatment.
Local political leaders lamented the lack of security provided to the Hazara people.
"For over 10 years, Lashkar-e-Jhangvi has been attacking Shiites in Quetta, but successive governments and law enforcement agencies have taken no notice," Abdul Khaliq Hazara, the chairman of Hazara Democratic Party, which represents the minority Hazara community, said in a telephone interview.
Mr. Hazara said Sunni militants received support from the Taliban from inside the province and from across the border in Afghanistan, and he accused "elements" within the law enforcement agencies of aiding them.
Separately, in a possible sign of lingering diplomatic tensions between Pakistan and the United States, the Pakistani government was reported to have issued new restrictions on the movement of American diplomats.
The Associated Press reported Saturday that the Foreign Ministry sent a letter to the American Embassy last month saying that American diplomats would be required to apply for permission to leave the capital at least five days before they traveled, even including visits to cities where the United States has consulates.
An American Embassy spokesman in Islamabad confirmed that a diplomatic note had been sent by the Pakistani government. "We are working with the Pakistani government to resolve the matter," the spokesman said.
But later Saturday, the Foreign Ministry issued a statement saying that "no U.S.-specific restrictions have been applied," noting that general guidelines to ensure the "safety and security" of diplomats "have existed for a long time."
The statement said that Pakistan was aware of its obligations under the Vienna Convention on Diplomatic Relations, and that it was "having a constructive engagement with the U.S. Embassy in Islamabad in this regard."
Relations between Pakistan and the United States have been strained since a Central Intelligence Agency contractor shot two Pakistanis in January, and worsened after the May 2 American raid to kill Osama bin Laden was conducted without alerting the Pakistani authorities.
First Published: July 31, 2011, 4:00 a.m.