Abu Anas al-Liby senior al-Qaida member worked at Pizza Restaurant

A son of the suspected senior al-Qaida member Abu Anas al-Liby has described the moment masked US commandos grabbed his father outside their Tripoli home.

Abdullah al-Ruqai, 21, said three masked men brandishing handguns leapt from a white Mercedes van as his father, whose real name is Nazih Abdul-Hamed al-Ruqai, returned in his car from morning prayers at 6.30am on Saturday in the leafy suburb of Noufle'een.

"Just as my father was parking, these cars came from everywhere," he said. "There were three white cars which blocked the street, then came the van, all of them with tinted windows. The van pulled up and 10 men got out; three of them had masks and handguns fitted with silencers."

The masked men ran to his father's car, a black Hyundai Tucson, smashed the driver's window with a gun and hauled open the door. "Some of the men were shouting 'get out, get out' in Arabic," he said. "They dragged my father out and threw him on the bonnet of the car. He was shouting 'what's going on?'"

Watching from the walled four-storey family home located on a street corner opposite a school, Abdullah saw his father dragged across the road to the van. "His body was floppy, he wasn't speaking, they must have drugged him."

In seconds the swoop was over. No shots were fired. Liby was pushed into the van, the doors slammed shut and it roared off followed by the three white cars.

Abdullah said he was sure that Libyan forces were involved in the operation, something the government has yet to clarify. "The guys in masks, they moved like professionals, like they knew what they were doing. But the other seven, they were standing back, they looked like amateurs, they shouted with Libyan accents and moved like Libyans. As a Libyan you just know."

He said proof would be provided when friends of his father release footage from a CCTV camera Liby had installed on the wall of the house.

"Ever since we moved back here my father feared he would be targeted," Abdullah said, standing by the Hyundai which was still missing its driver's window. "We all expected we would be bombed by plane, we didn't think they would come for him like this."

He said the arrest brought back memories of witnessing his father's arrest by British police in their home in Manchester when he was nine years old. He remembered police kicking in the door early one morning and hauling his father away. "It was bad, I remember it clearly, all the shouting, all the noise."

Abdullah said his father was innocent of US accusations that he helped mastermind the bombing of the American embassy in Nairobi with the loss of more than 200 lives in 1998.

He said his father had no connection with Osama bin Laden. "He never met Bin Laden, he never worked with him, he was not a terrorist," he told the Guardian. "As a young man, he went to fight the Soviets in Afghanistan. He heard how people were being killed, women raped in Afghanistan and he wanted to help."

Abdullah, a high school student, said the family left England for Iran, living there for six months before they were all arrested and held for seven years. "The Iran arrest was worse than the one in Manchester. In Iran we were kept underground, we hardly saw the daylight."

In 2010 Iran allowed the family to return home without Liby. He followed them later, arriving in time to participate in the Arab Spring uprising in which the oldest of his four sons was killed. "He fought against the Gaddafi forces in the Nafusa mountains. Later he was in the assault on Bab al-Aziza [Gaddafi's Tripoli compound]."

He said his father taught each of his four sons to memorise the Qur'an. "He was a good Muslim. In Manchester he did not encourage us to follow football, he wanted us to learn the Qur'an."

Liby planned to clear his name of criminal charges and resume his work as a computer expert specialising in nuclear research, but also prepared his family for the worst. "My father feared he could be kidnapped at any time, he brought each of us up to be ready to be the leader of the family. And now that person is me," Abdullah said.