BEIRUT: ISIS fighters have killed at least 400 people, including women and children, in Palmyra since capturing the ancient city four days ago, Syrian state media said Sunday. It was not immediately possible to verify the account, but it was consistent with reports by activists that the Islamist fighters had carried out extra-judicial executions since capturing the Syrian city from government troops.

Some anti-regime activists in Syria, however, disputed the account, saying that the victims were regime informers and soldiers.

The militants Wednesday seized the city of 50,000 people, site of some of the world’s most extensive and best preserved ancient Roman ruins.

“The terrorists have killed more than 400 people including women and children ... and mutilated their bodies, under the pretext that they cooperated with the government and did not follow orders,” Syria’s state news agency said, citing residents inside the city.

It added that dozens of those killed were state employees, including the head of the nursing department at the hospital and all her family members.

ISIS supporters have posted videos on the Internet they say show fighters going room to room in government buildings, searching for government troops and pulling down pictures of President Bashar Assad and his father.

Activists have said on social media that hundreds of bodies, believed to be government loyalists, were in the streets.

The Britain-based Syrian Observatory for Human Rights said a number of people were beheaded in the town since it fell but has not given an estimate for the toll among civilians.

It says at least 300 soldiers were killed in the days of fighting before the city was captured.

“A bigger number of troops have disappeared and it is not clear where they are,” Observatory director Rami Abdel-Rahman told Reuters.

Elsewhere, the jihadis shot down a government helicopter in the north of the country, according to both the Observatory and supporters of ISIS.

But state media said the helicopter had suffered technical problems.

The Observatory said ISIS brought down the helicopter after midnight near the Kweiris air base in the eastern part of Aleppo province.

Abdel-Rahman said at least one crew member had been killed but “the fate of the rest is unknown.”

Jihadi accounts on Twitter said ISIS had downed the helicopter using anti-aircraft missiles. They posted the names of three crew members they said had been killed, along with pictures of a helicopter in flames.

ISIS fighters have surrounded the air base since March 2014.

Also, Syrian state television said its air force had killed 300 insurgents in strikes that broke the siege of the Jisr al-Shughur hospital in northwestern Idlib province.

Dozens of Syrian troops evacuated their positions Friday after holding out for nearly a month in the face of a rebel siege, and most of them were killed in the attempt to break out, according to opposition sources. Separately, the Ahrar al-Sham Islamist militia said it assassinated a brigadier general and six of his bodyguards Sunday in an explosion in Damascus. It posted a video online claiming to show the attack on Brig. Gen. Bassem Ali Muhanna’s car with an improvised explosive device. A security source said Muhanna was a member of the elite Republican Guard.