At least eight Shia Muslims have been killed and 10 others wounded after suspected Sunni extremists opened fire on them in the southwestern Pakistani city of Quetta, police say.

Hamid Shakil, a police official, said the victims were in a neighbourhood park when they were shot at on Friday.

He said the assailants fled after the attack, the first since the killing on Monday by US forces of Osama bin Laden, the leader of al-Qaeda, in the Pakistani garrison town of Abbottabad.

"They were taking morning exercise when the attackers came in two cars and indiscriminately opened fire on them," he told the Reuters news agency.

He quoted residents as saying the attackers fired rockets before shooting.

Sunni extremists often attack Shias, whom they view as heretics.

The killing of bin Laden has triggered fears of a backlash from Sunni groups operating in the country, many of them with ties to al-Qaeda.

No one has claimed responsibility for the latest attack.

In January a teenage suicide bomber blew himself up near a Shia Muslim procession in the city of Lahore, killing at least 10 people and wounding more than 50.

Officials have blamed most of previous attacks on Lashkar-e-Jhangvi (LeJ), a Pakistani group allied to al-Qaeda.

Shias roughly account for up to 20 per cent of Pakistan's mainly Sunni Muslim population of 170 million.

Meanwhile, US drone aircraft fired missiles into a house in Pakistan's North Waziristan region on Friday, killing at least eight suspected militants, local intelligence officials said.

Ties between the two supposed allies have been strained over drone attacks that target extremists linked to al-Qaeda but have killed dozens of civilians.

And since August 2008, there have been over 250 drone attacks that have reportedly killed more than 1,500 people in north and south Waziristan.

A major protest in the northwestern city of Peshawar was staged last week by cricketer-turned-politician Imran Khan to put pressure on the US to prevent the unmanned aerial vehicles from killing civilians.

Source: Agencies