Pakistani security agencies have arrested five Al Qaeda-linked terrorists who were plotting suicide attacks on key installations in the country.

The targets included the President's Office, Prime Minister House, the US embassy in Islamabad, and General Headquarters, Chief of Army Staff House and Lal Haveli in Rawalpindi, Information Minister Sheikh Rashid Ahmed said.

The arrests were made over the past week in different parts of the country, he added.

The masterminds were two Egyptians identified as Qari Ismael and Sheikh Essa, who continued to be at large, Information Minister Sheikh Rashid Ahmed said.

The Egyptians belonged to Al Qaeda, Interior Minister Faisal Saleh Hayat said.

"We hope to catch him and the rest of the gang members soon," APP news agency quoted him as saying in Lahore.

A lot of arms and ammunition, including bombs, grenades, rockets, rocket launchers, detonators and around 50 other explosive devices were seized, Ahmed said.

The conspiracy, if successful, could have killed hundreds of people, he said.

"These people were planning to carry out destructive and bloody terrorist attacks during a weeklong time starting from August 13," he said.

"We are looking for three or four more suspects in connect with the plot."

Hayat said the arrests were made between August 11 and 15, but gave no reason why the announcement was delayed.

The haul is the latest in a crackdown on Al Qaeda suspects launched in mid-July.

Since then more than 60 have been taken into custody from different parts of the country.

Among those earlier arrested were Al Qaeda's Pakistani computer whiz Naeem Noor Khan and Tanzanian Ahmad Khalfan Ghailani, suspected of involvement in the 1998 bombing of US embassies in East Africa.