Four men appeared in a London court on Saturday charged with terrorism offences after being arrested as part of a major police investigation linked to Pakistan.

The men, from Birmingham, were detained on Tuesday in a counter-terrorism operation which has seen eight others already charged, including three who are alleged to have been plotting a suicide bomb attack in Britain.

Khobaib Hussain, Ishaaq Hussain and Shahid Kasam Khan, all 19, and Naweed Mahmood Ali, 24, are accused of fundraising for the purposes of terrorism, travelling to Pakistan for training and travelling abroad to commit acts of terrorism.

They were remanded in custody following a hearing at Westminster Magistrates' Court and will appear again at Kingston Crown Court on December 9, the Press Association reported.

Police said their arrests had been pre-planned and not made in response to any immediate threat to public safety.

Britain's security services have been on high alert since four British suicide bombers killed 52 commuters on three trains and a bus in London on July 7, 2005. A similar attack failed two weeks later when the bombs did not explode.

The government said in July that the threat level had been downgraded by one notch to substantial, the third highest of five categories, meaning an attack is a strong possibility.

(Reporting by Tim Castle; Editing by Mark Heinrich)