LONDON - British police said Saturday they had released one of four men arrested during a dramatic counter-terrorism operation in London a week ago.

The 29-year-old man, a Briton of Pakistani origin, had been held during a string of raids last Sunday that included armed officers shooting out the tyres of a car near the Tower of London.

"Three men remain in custody," London's Metropolitan Police said in a statement, adding that the fourth man has been released without charge.

They include two 25-year-old Britons, one of whom is of Turkish origin and the other of Algerian descent.

They were arrested on Sunday evening after police shot at their car with Hatton rounds - special shotgun ammunition used to breach doors and tyres - 200 metres from the Tower of London, one of London's busiest tourist attractions.

The third suspect is a 28-year-old Briton of Azerbaijani origin who was shown on CCTV footage being wrestled to the ground by police. The three remaining suspects were continued to be held at a south London police station on suspicion of the commission, preparation or instigation of acts of terrorism.

Police have until Sunday night to question them, after which they can apply for another seven-day extension.

The BBC quoted unnamed officials as saying the suspects were accused of a "serious" jihadist plot involving the use of firearms.