A woman was arrested in London Saturday on suspicion of terrorism offences in an operation that saw six men detained earlier this week but which police say is not linked to the Olympics.

Officers from Scotland Yard's counter-terrorism command arrested the 22-year-old in an early morning raid at a home in Hackney, northeast London.

She was held "on suspicion of the commission, preparation or instigation of acts of terrorism" and remains in custody, London's Metropolitan Police said in a statement.

The arrest was part of an ongoing investigation in which five men and a woman were arrested on Thursday, police said, adding that the operation is not linked to the London Olympic Games which begin on July 27.

Ahead of the Games, Britain's security threat level is set at "substantial," meaning officials believe there is a strong possibility of a terror attack.

Five men ranging in age from 18 to 29 and a woman aged 30 were arrested Thursday and all six are being held on suspicion of terrorism offences.

Police on Friday obtained warrants for further arrests that will expire next Thursday.

Scotland Yard declined to elaborate, but British media reported that the arrests related to a possible plot involving Islamist extremists with potential targets in Britain.

The latest detentions come on the seventh anniversary of the July 7, 2005, attacks, when four suicide bombers targeted London's transport network, killing 52 people and injuring more than 770.

In a separate investigation, seven people were arrested over the past week after police found weapons hidden in a car on a motorway in Yorkshire, northern England.