Police said Friday they had arrested four terror suspects near London's Heathrow airport, where the army has deployed hundreds of troops because of fears of an attack.
Thames Valley Police on Thursday arrested four suspects in Langley, some five miles west of Heathrow.
Police didn't give details about the suspects or say if any weapons were found. They refused to say whether the arrests were connected to the security alert at Heathrow and in the London area since Tuesday.
The suspects were being questioned, and local officers were in contact with the anti-terrorist unit at Scotland Yard, police said.
Officers also continued to question a 37-year-old Venezuelan man Friday after he was arrested at London's Gatwick airport for carrying a suspected live hand grenade in his luggage. He arrived on a flight from Caracas on Thursday afternoon, and his arrest led officers to shut the airport's North Terminal for several hours.
Police were also questioning two men detained Thursday in Hounslow, near Heathrow. Police did not believe they were linked to the threat to the airport, which is Europe's busiest.
At Stansted airport north of London, police shut an access road to the terminal building Friday because of the security measures, but reopened it at around 9:30 a.m.
Police have warned that Usama bin Laden's Al Qaeda network might try attacking London during this week's Muslim festival of Eid al-Adha. The warning prompted visibly higher security at major airports and in the center of the capital.
"We're taking every measure necessary to keep London safe and the evidence of our activity is out there on the streets," Andy Trotter, the Metropolitan Police's deputy assistant commissioner, told the British Broadcasting Corp. on Friday.
Trotter said tighter security would continue for "as long as is necessary."