The United States has evacuated all non-emergency staff from its consulate in the Pakistani city of Lahore, citing "specific threats" amid a worldwide alert over al-Qaida intercepts.

People rush an injured man to a hospital in Quetta, Pakistan, on Friday. Gunmen opened fire on worshippers outside a mosque, killing at least nine people and wounding 27 in the attack. Arshad Butt / Associated Press

The US State Department also reiterated a longstanding warning to US citizens to avoid all non-essential travel to Pakistan in a statement issued on Thursday.

The move came as Pakistan's troubled southwestern city of Quetta, focus of a surge in sectarian bloodshed, was hit by its second attack in two days as gunmen shot dead at least nine people and injured 27 outside a mosque on Friday.

The worshippers were gunned down as they left prayers for Eid al-Fitr, the festival marking the end of the Islamic holy month of Ramadan, which was marred in Pakistan this year by at least 11 attacks that killed 120 people.

A suicide bomber struck at a police funeral in the city on Thursday, killing 38 people in an attack claimed by the Taliban that will raise yet more concerns about the violence that has continued unabated since the newly elected government took office.

The closure of the US consulate in Pakistan's second-largest city and cultural capital came amid heightened security measures in Islamabad, where police and soldiers were maintaining a highly visible presence on the streets.

Meghan Gregoris, spokeswoman for the US embassy in Islamabad, said the evacuation was not linked to a terror threat that prompted the closure of 19 diplomatic missions in the Middle East and Africa.

"We received information regarding a threat to our consulate in Lahore. As a precautionary measure we have undertaken a drawdown for all but emergency personnel in Lahore," she said.

Timetable uncertain

The US embassy and consulates in Karachi and Peshawar were closed on Friday for the Eid al-Fitr public holiday but are expected to open again on Monday, she said. The Lahore mission was likely to remain closed and there was currently "no indication" of when it might reopen.

"We will continue to evaluate threat-reporting and take decisions as appropriate," she said.

Despite Pakistan's fractious alliance with the US in the "war on terror", anti-US sentiment runs deep in the restive, nuclear-armed country, fueled in part by the CIA's campaign of drone strikes against militants in the tribal northwest.

Washington maintains the strikes are an important and effective weapon in the fight against Taliban and al-Qaida militants. Pakistan publicly denounces the strikes as a violation of sovereignty.

US diplomatic missions have been targeted in the past.

A suicide car bomber rammed a US diplomatic vehicle in Peshawar in September, killing two people. It was at least the third time the mission and its staff had been attacked by Taliban and al-Qaida-linked militants since April 2010.

This week's closure of US missions mainly in the Arab world was reportedly ordered after messages from al-Qaida leader Ayman al-Zawahiri to the terror network's Yemeni franchise were intercepted.

The alert focused on al-Qaida in the Arabian Peninsula, a Yemen-based group that has made several attempts to attack the US in recent years and is widely seen as the group's most sophisticated offshoot.

On Tuesday, the US and other Western countries withdrew diplomatic staff from Yemen, where the US is fighting a drone war against the al-Qaida regional affiliate.

US officials have said al-Qaida's core leadership in Afghanistan and Pakistan has been decimated in recent years. They cite the 2011 killing of Osama bin Laden and the killing of several senior operatives in US drone strikes.

AFP-Reuters