(Women stand outside the Rida mosque which has been set on fire in Anderlecht commune in the west of Brussels March 13, 2012. REUTERS/Yves Herman )

A firebomb attack on a Shi’ite Muslim mosque in Brussels that killed a popular local imam triggered an anti-terrorist investigation on Wednesday, but police remained uncertain of the detained suspect’s identity and local Muslims baffled about his motives.

Prosecutors have released few details about the suspect, a man in his 30s who locals said entered the mosque in a rundown quarter of the city shortly after evening prayers on Monday carrying an axe, a knife and a can of petrol, which he poured over the prayer mats and ignited.

“He is saying he is a Salafi Muslim,” federal prosecutor Leen Nuyts told Reuters, adding that it was one of several explanations he had offered. “He is saying that Syria could have played a part, but we have to do further investigation” before reaching that conclusion, she said.

Nuyts said the suspect had provided three different identities and efforts were still being made to establish which was correct. Locals said he was a Sunni Muslim Moroccan from Tangiers.