British counter-terror detectives say they've arrested a 61-year-old man and a 53-year-old woman as they investigate the slaying of a Syria-born Muslim cleric who was shot in London.

Scotland Yard's Counter-Terrorism Command said Thursday the man was arrested on suspicion of conspiracy to murder Abdul-Hadi Arwani and on suspicion of commission, preparation and instigation of acts of terrorism. The woman was arrested on the terror charge. No details were offered as to what the terror charges entailed.

Both remain in custody at a south London police station.

Another man, Leslie Cooper, 36, was charged on Monday with the murder of Arwani, a former imam at An-noor mosque in Acton, west London.

Arwani, 48, was found in a parked car with gunshot wounds in the Wembley area.