ISLAMABAD - PAKISTANI authorities placed the country's airports on 'red alert' on Thursday after Islamabad's international terminal received a telephone threat warning of a possible bomb attack, officials 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 ordered a red alert at all airports following the threat received at Islamabad airport,' a senior Airport Security Force official told sources on condition of anonymity.

Flights were however operating as normal, the official said.

Security officials were carrying out a search operation at Islamabad's Benazir Bhutto international airport after receiving a warning about a possible suicide attack.

'We received a call this morning that a bomb attack was expected around midday,' an Islamabad airport security official told sources, adding that the threat was being taken 'seriously'.

'We were already alert and have now further beefed up security at the airport,' the official said.

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

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 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.

Islamabad itself has been under very heavy security since the deadly Marriott bomb, which turned the landmark building into a charred shell and sparked fears of further attacks. -- AFP