Yemen security source: Dozens of Al Qaeda arrived in capital recently to prepare for attack

He says a security source confirmed that Yemeni intelligence services had discovered that dozens of al-Qaeda members had arrived in Sanaa over the past days in preparation for a major attack.

The source suggested it was to include explosions and suicide attacks aimed at Western diplomatic missions and Yemeni military headquarters.

Checkpoints have been set up across the city and senior officials are being advised to limit their movements.

Amid the escalating tensions, sources also told BBC Newsnight that the US was preparing special operations forces for possible strike operations against al-Qaeda in Yemen.

Although the US has previously sent special forces to train counter-terrorist units, there are now suggestions that the Joint Special Operations Command (JSOC), may be preparing units for strike operations, the sources said.