Kurdish authorities in northern Syria have imposed a one-week curfew in certain areas that they recently captured from the Islamic State group, an activist group said Tuesday.

The Britain-based Syrian Observatory for Human Rights said the curfew will begin on Wednesday and will apply to Kurdish-held areas in Raqqa province and the outskirts of the nearby town of Ras Al-Ayn. It said people who plan to move during this period will have to get approval from the local Kurdish police force known as "Asayish."

Members of the Kurdish People's Protection Units, or YPG, have captured large parts of northern Syria from IS in recent months under the cover of airstrikes by the U.S.-led coalition. Counterattacks by the extremists have left scores dead.

On Monday, IS fighters captured the town of Ein Issa and nearby villages in a surprising attack on Kurdish forces, two weeks after the YPG captured the town.

In another push, IS fighters last month attacked the northern Syrian town of Kobani, killing more than 200 people in the town that became a symbol of Kurdish resistance against extremists. Fighting continued for days until IS militants were killed or surrendered.

Juan Mohammed, a Kurdish official in northern Syria, had no confirmation about the one-week curfew, but said the move makes sense and there have been curfews imposed in other areas under YPG control recently.

"We are in a state of open war and caution is important. Such measures should be taken to prevent infiltrations," Mohammed said.

The Observatory said 78 IS fighters have been killed since Sunday either in clashes with the YPG or by airstrikes from the U.S.-led coalition.

On Monday, YPG spokesman Redur Khalil said that during the month of June, 483 IS fighters were killed in clashes with Kurdish fighters. He added that the YPG has the bodies of 223 IS militants as well as six prisoners.

Khalil said 62 YPG fighters were killed in June in 44 battles they fought against IS.

Also Tuesday the World Food Program said that along with a local partner they made a breakthrough delivery of urgently needed food assistance in Raqqa province after more than eight months of disrupted access to the governorate.

The WFP said the distribution occurred in the border town of Tal Abyad that was captured last month by Kurdish fighters from IS.

It said a convoy carrying 2,000 food rations in support of 10,000 people arrived in Tal Abyad Thursday from the northern Syrian town of Qamishli. WFP added that on the same day, 2,000 monthly food rations were distributed to families in need.