ISLAMABAD: Pakistan placed all airports on red alert on Thursday after a telephone caller warned of a suicide bomb threat to Islamabad's international airport, officials said.

Passengers were briefly evacuated from the capital's Benazir Bhutto airport while security officials searched the area, but all flights were operating as normal, they said.

The security boost comes just days after a massive suicide truck bombing at the Marriott Hotel in the capital on Saturday left 60 people dead and more than 260 wounded.

‘We have raised the security level to red alert. It was already on high alert but after the bomb threat in Islamabad we stepped it up,’ senior airport security force official Mohammad Irfan told AFP.

British Airways cancelled its six weekly flights to Islamabad earlier this week, citing security reasons.

In Islamabad, officials said security had been massively stepped up at the entrance and exit gates after a caller made a specific warning about an attack on the airport on Thursday.

‘The airport received a telephone threat that a bomb could go off inside the building about midday,’ Islamabad airport official Mohammad Malik told AFP.

‘Passengers were evacuated for a short time for debriefing on measures that security forces were taking because of the threat but then they were allowed to return. But there was no delay to flights,’ Malik said.

Road traffic to the airport was suspended for a short time.

In February 2007 a suicide attacker opened fire near the VIP area of the same airport before blowing himself up with a hand grenade, injuring three people.

The airport, which was recently renamed after slain former premier Bhutto, is located on the outskirts of the garrison city of Rawalpindi, about 12 kilometres from Islamabad, and is outside the main security cordon for the capital.

The US embassy in Islamabad announced on Thursday it was halting its consular services amid the turmoil.

‘The embassy is temporarily suspending routine consular services including visa services beginning Thursday. Emergency American citizens' services will continue to be available,’ spokesman Lou Fintor told AFP.

He said the embassy had also banned staff from staying at major hotels in the eastern city of Lahore, following similar edicts for Islamabad, Karachi and the northwestern city of Peshawar.