An aide to a senior Yemeni government military adviser and three security guards have been wounded in an explosion.

It was not immediately clear who planted the bomb on a road in the capital Sanaa then detonated it as Fawaz al-Dhibri's vehicle went past. All four victims were yesterday in a stable condition in hospital.

Yemen has been plunged into turmoil since pro-democracy protests in 2011 forced president Ali Abdullah Saleh to step down after 33 years in office. Authorities have since struggled to rein in rival political factions and tribes.