One of the Syrian regime's most notorious prisons has been demolished by Islamic State jihadists in the city of Palmyra.

The Syrian Observatory for Human Rights said that IS militants had blown up the prison, which was for decades one of the regime's most feared detention centres.

There are concerns that the jihadists might also destroy the ruins of the ancient World Heritage site of Palmyra, which the group captured from Syrian government forces 10 days ago.