Pakistani police foiled planned suicide attacks on the twin cities of Islamabad and Rawalpindi, arresting six suspects and seizing three vehicles packed with explosives, officials said yesterday.

The arrests came days after al Qaeda carried out a suicide car bomb attack on the Danish embassy in Islamabad on Monday that killed six people, all of them Pakistani. The arrests were made late on Thursday in the garrison town of Rawalpindi, the city neighbouring the capital.

The arrests triggered a high alert in the two cities. Security was tightest along Islamabad's Constitution Avenue, the duel carriageway leading to the presidency building, National Assembly, Supreme Court, various ministries and the diplomatic enclave where many embassies are located.

Concrete barriers were placed across the broad avenue, and regular entry points to the enclave were closed, while razor wire was laid around the perimeter of key buildings.

The Danish mission, which had been under threat ever since the publication of cartoons of the Prophet Mohammed by Danish newspapers in 2005, was located in a plush residential neighbourhood. A Danish team has arrived in Pakistan to work with agents investigating the attack on its embassy.

The Netherlands mission has moved to a hotel with tight security, having come under a similar threat to the Danes because of a film made by a Dutch anti-immigration politician that is deemed offensive to Muslims.