Pakistani security agencies seized three explosive-laden vehicles and arrested five persons in the garrison city of Rawalpindi, prompting officials to further tighten security in the nearby federal capital on Friday.

The cars were seized in Dhoke Kala Khan area, city police chief Rao Mohammed Iqbal said. Other officials said the vehicles contained over 1,000 kg of explosive materials and were seized late Thursday night and early this morning.

The explosives were defused shortly after the vehicles were impounded. The five arrested men were taken to an undisclosed location for interrogation.

Security officials were quoted by TV channels as saying that the men had planned to target key sensitive installations and high-value targets, including possibly President Pervez Musharraf's [Images] camp office in Rawalpindi.

The arrests were made four days after a suicide bomber blew up his explosive-laden car outside the Danish embassy in Islamabad, killing eight persons and injuring 24.

The government called in additional paramilitary forces to provide protection to diplomats in Islamabad in the wake of the suicide car bombing.

Al Qaida has claimed responsibility for the blast, saying it was carried out with the assistance of Pakistani mujahideen to protest re-publication of blasphemous cartoons of Prophet Mohammed in Danish newspapers earlier this year.

Following the seizure of the explosive-laden cars, security was further tightened across Islamabad, including the Constitution Avenue.