More than 1,000 people are believed to have died so far in fighting between security services and Assad loyalists

Clashes between Syrian security services and fighters loyal to the ousted Assad regime erupted on Wednesday, kicking off five days of still-ongoing fighting which has left more than 1,000 dead, including 745 civilians, according to a war monitor.

The clashes, some of the deadliest the country has seen since the beginning of its civil war in 2011, were the biggest challenge Syria’s new authorities has faced since taking power in December.