Intelligence agents seized seven conspirators in central Punjab province in late April, around a week before the capture on Monday of Abu Faraj al-Libbi, allegedly a key aide of Usama bin Ladin, officials said on Saturday.
The Libyan, accused by military leader Musharraf of masterminding two earlier attempts to blow him up in December 2003 because of his support for the US-led "war on terror", had links with the assassination plotters, they added.
"This is a spectacular achievement by Pakistan's security agency," said one top security official. "First we smashed the gang plotting a new attack on Musharraf and then, a week later, we netted two Arabs including al-Libbi."
Officials said the suspects involved in the latest bid were headed by a Pakistani al-Qaida fighter freed from prison in Afghanistan named Mohammad Arshad, who is an associate of al-Libbi.
Also among them was junior air force official Mushtaq Ahmed, who escaped from jail last November after being sentenced to death for a key role in one of the earlier attempts on Musharraf's life.
He was recaptured last week.
"The group was planning a new attack on President Musharraf in Rawalpindi or Islamabad. They had assembled the explosive devices and they were to use them adopting a new method," the intelligence official said, without giving details.
Pakistanis read about the latest
arrests after al-Libby's capture
The plot was revealed when security agencies arrested Ahmed, the official said.
"Mushtaq Ahmed was an important part of the group and we understand that the group's leader was in contact with al-Libbi," the official added.
A security official said it was possible al-Libbi's arrest in Mardan town in North West Frontier Province was based on intelligence gleaned from those arrested in Punjab.
The identity of the other Arab had not been established, but he appeared to be a mid-level operator, he added.
Ten Afghans were also picked up.
In December 2003, anti-Musharraf elements blew up a road bridge moments after he passed and then two weeks later, on Christmas Day, car bombers ploughed into his motorcade in the same area, killing 15 people.
Abu Faraj al-Libbi is believed to
have been a key bin Laden aide
Ahmed was convicted of a role in the first attack in November and escaped from military custody soon afterwards. Security forces arrested him on a tip-off last week on a bus south of Islamabad.
Prime Minister Shaukat Aziz said on Friday the interrogation of al-Libbi was "proceeding well", while another security official said he was being questioned to get more leads on his accomplices.
Al-Libbi took over al-Qaida operations in Pakistan after the arrest in March 2003 of Khalid Sheikh Mohammed, the key planner of the 11 September attacks and the network's former number three, officials said.