ISLAMABAD, May 6: Key Western and allied diplomatic missions in Islamabad have adopted strict security measures in the wake of foreign intelligence agencies' warning of possible terror attacks in Pakistan.

Diplomatic sources told Dawn on Thursday that at least two key Western embassies received warnings of possible terror attacks targeting foreign missions on Monday and heightened security for their staff and premises in view of the information received.

The Australian High Commission closed down its immigration section on Wednesday and the US government temporarily shut down the American Centre and relocated its staff at US embassy premises due to security concerns.

Diplomatic sources said at least one European mission had been informed by its intelligence agencies at home that Al Qaeda operatives could target Western diplomatic missions using diplomatic car registration plates to deceive security staff at the entrance of the diplomatic enclave.

These sources claimed that the information had been passed on to Pakistani authorities. Foreign Office confirmed that key Western missions had heightened security.

Foreign Office spokesman Masood Khan told Dawn on Thursday that following rumours about the closure of the Australian mission, High Commissioner Howard Brown informed the Foreign Office that the mission's immigration section had been closed down as a precautionary security measure.

He said the Australian High Commissioner had told the Foreign Office that these measures would be relaxed as soon as possible. The Foreign Office spokesman said the Australian High Commissioner also clarified that the step had nothing to do with the wheat consignment controversy.

Dawn learnt through diplomatic sources that the British High Commission has also delayed the opening of its visa sections in Karachi and Lahore. The top British intelligence agency MI5 has warned the British mission in Islamabad of threat of an attack under the diplomatic cover.

This information was conveyed to the British High Commission this Monday and from Tuesday it went from a low security to a high security grade. "Internally we are treating it as red alert," an informed source told Dawn.

According to diplomatic sources the British High Commission has also postponed the opening of its visa office in Karachi, which was otherwise scheduled to open by May 15.