Local security forces in Syria's northern city of Raqqa announced a two-day curfew starting Sunday in response to intelligence on potential attacks by the Islamic State group.
IS was kicked out of its former bastion Raqqa in October by the US-backed Syrian Democratic Forces, which then stood up police units to hold the city.
On Sunday, the Raqqa Internal Security Forces said it had received "information that terrorist groups working on behalf of Daesh (IS)... have entered Raqqa city to carry out attacks against stability and security".
It therefore decided to put in place "a state of emergency and a curfew in Raqqa city starting at 5:00am (0200 GMT) on Sunday June 24, 2018, until 5:00 am on Tuesday."
IS lost its de facto Syrian capital of Raqqa after four months of ferocious fighting and bombing by the SDF and the US-led coalition that left the city in ruins.
The SDF has since whittled down IS territory elsewhere in Syria's north and east to just a handful of isolated pockets.
But in the meantime, security incidents around Raqqa have been on the rise in recent weeks.
On Friday, IS claimed its first attack in Raqqa province since being ousted, announcing through a propaganda media channel that it had detonated a roadside bomb northeast of the city.
An SDF fighter was also killed on June 15 at a checkpoint north of Raqqa, in what the Syrian Observatory for Human Rights said was an IS attack.
The group did not claim responsibility for that incident.
And earlier this month, five police officers linked to the SDF were killed in a roadside blast during a routine patrol in Raqqa city, though no one claimed that attack either.