Large blast heard in Afghan capital

The cause of the blast was not immediately known but sirens could be heard wailing in the central district that houses the embassies of the United States, Britain and other missions.

Violence in Afghanistan has reached its worst levels in a conflict now more than eight years old, with Taliban insurgents spreading their attacks to previously secure areas. This year has also been the deadliest for Western troops in the country.

The mounting violence comes at a time U.S. President Barack Obama is considering whether to send up to 40,000 more troops to Afghanistan as requested by his top commander there, General Stanley McChrystal.

There are now more than 100,000 Western troops serving in Afghanistan, two-thirds of them American.

(Writing by Jonathon Burch; Editing by Sanjeev Miglani)

(For more Reuters coverage of Afghanistan and Pakistan, see: http:/www.reuters.com/news/globalcoverage/afghanistanpakistan)