Australian Doc Among 3 Latest Arrests

An armed police officer patrols in Whitehall, central London, Sunday, July 1, 2007. Britain has moved to the highest level of terror alert, 'critical', after two car bombs were defused in the capital on Friday, and a suspected terrorist attack on Glasgow airport on Saturday. (AP Photo/Simon Dawson) (Simon Dawson - AP)

Two U.S. counterterrorism officials, who agreed to discuss the case only if not quoted by name, said the attackers in Britain were Islamic extremists sympathetic to al-Qaida, but investigators were still trying to figure out whether there were any direct links.

One of the officials also said there continued to be concerns about possible plots to attack the United States, including the potential for a large-scale assault by al-Qaida. Among the factors contributing to the worry are al-Qaida's efforts to recruit in Pakistan's tribal areas and its increased flow of public messages, the official said.

In the latest attacks, two car bombs failed to explode in central London on Friday and two men rammed a Jeep Cherokee loaded with gas cylinders into the entrance of Glasgow International Airport and then set it on fire Saturday.

The British government security official said investigators were working on one theory that the same people may have driven the explosives-laden cars into London and the blazing SUV in Glasgow.

The unidentified driver of the Jeep was being treated for serious burns at Royal Alexandra Hospital in Glasgow, where he was under arrest by armed police. Bomb experts carried out a second controlled explosion on a car at the hospital Monday, after a similar blast Sunday. Police said the car was linked to the investigation, but no explosives had been found.

Police announced Monday that they arrested two men the previous day at residences at the hospital, but would not say whether they were doctors. Britain's Sky Television described them as trainee physicians, without citing a source for its report.

Four men and a woman were detained earlier.

Authorities identified Bilal Abdulla, an Iraqi doctor who worked at the Glasgow hospital, was the other man arrested at the airport and said he was being held at a high-security police station in Glasgow.

According to the British General Medical Council's register, a man named Bilal Talal Abdul Samad Abdulla was registered in 2004 and trained in Baghdad. Staff at the Glasgow hospital said Abdulla was a diabetes specialist.

A man arrested late Saturday on a highway in central England was also a physician, Mohammed Jamil Abdelqader Asha, police said. A Jordanian official said Asha was of Palestinian descent and carried a Jordanian passport.

Britain's The Independent and The Muslim News newspapers reported that a man arrested in Liverpool late Saturday was a 26-year-old doctor from Bangalore, India, who worked at Halton Hospital in Cheshire, northern England. Police would not immediately comment on the reports.

The Muslim News also said the Indian doctor had used the car, cell phone and Internet account of a fellow physician who had moved from England to Australia around a year ago. It said police had asked friends of the Indian for details about the man who went to Australia.