ISLAMABAD/PESHAWAR, Aug 11: A British national, Rashid Rauf, who was arrested by an intelligence agency provided a lead to thwart the plot to blow up trans-Atlantic flights, sources said.

The sources said Rashid Rauf was father of Tayyab Rauf, a suspect who was arrested in United Kingdom last year in connection with 7/7 London train blasts.

During interrogation, the suspect unveiled the terrorism plot aiming to destroy at least ten passenger aircraft in the UK, the sources said.

They said the information was shared with the UK Home Land Security department that resulted in a raid in which 21 suspects were arrested in London on Thursday.

The links of the arrested suspect could not be confirmed, but the sources said intelligence agencies had put four Islamic organisations on the watch list, they included two UK-based outfits Al Mahajroon and Hizbul Tehrir, and two Pakistani organisations Lashkar-i-Taiba and Lashkar-i-Jhangvi.

The arrested suspect was stated to be under surveillance and his telephones calls and internet communications were being monitored for the last six months, the sources said.

The security agencies have so far arrested nine suspects and seven of them were netted on Friday from different parts of the country, including Islamabad, for their alleged links with the London terrorism plot. Three of the suspects were caught from Islamabad Airport on Friday morning, but their identification and details of their destinations could not be ascertained.

The sources said four suspects were apprehended from a village near Jhelum in a raid that was conducted on the information of the British High Commission in Islamabad.

Out of the seven suspects, two have been identified as Mohammad Al Ghadar and Ahmed Al Khan.

The UK government had arrested some 21 suspects from London on Thursday allegedly involved in the plot.

Sources said that several of plotters had travelled to Pakistan within the last couple weeks and had met at least one suspected Al Qaeda operative, most likely Mr Rashid Rauf.

Sources said the MI 5, which is responsible for operations within the UK had identified the suspect and his trail was later picked up by the ISI and Britain’s external espionage service MI 6, when he left the UK and was put under surveillance.

These sources said that the plotters were planning to carry out a dry run of the operation in the next days when they were rounded up. Had the dry run that included an attempt to board the flights at the same time proved successful, they were to carry out the real attacks within days of the dry run, these sources said.

Sources added that some Pakistanis had also been detained in connection with the airline terror plot and efforts were being made to get others still at large.

They said they were also trying to figure out who were the others the plotters or the key suspect got in touch with during their stay in Pakistan and retrace their steps. “It has all the hallmarks of Al Qaeda and Mr Rauf has had linkages across the border in Afghanistan,” the source said.

Interior Minister Aftab Ahmed Khan Sherpao, while talking to a group of reporters on Friday, confirmed the arrests of some suspects but he was reluctant to disclose their identifications and links. “If we disclose their names at this stage, it would harm the investigations,” he said.

He said Pakistan was fully cooperating with the UK in the arrests of suspects and investigation of the case to shatter the network involved in the UK terrorism plot.