An Iraqi Shia militia, backed by Iran’s Revolutionary Guards, says more than 110 of its fighters have been killed or wounded by a US attack in Iraq near the Syrian border on Monday.

The Kataib Sayyid al-Shuhada militia said in a statement, “We hold the American army responsible for this act,” adding that “smart rockets” were used. A spokesman said 36 fighters — including several Revolutionary Guards — were killed and 75 others wounded.

Abu Ala Welayi, the leader of Kataib Sayyid al-Shuhada, told Iran’s Tasnim News Agency that the US and Islamic State jointly attacked. He raised the death toll to 47 and said seven Revolutionary Guards were killed, including chief commander and strategist Hossein Qomi.

The US-led coalition said the claims were “inaccurate”, as it was not carrying out air attacks in the area at the time.

Iraqi Prime Minister Haider al-Abadi supported that version, saying an initial investigation showed that the Islamic State “carried out a breach using artillery and car bombs”.

And so did the Islamic State, which claimed responsibility and said it captured armored vehicles, weapons, and ammunition.

The attack on the militia was just across the border from the Free Syrian Army base, where US special forces are present, near Tanf in eastern Syria. The US has declared a 55-km (34-mile) exclusion zone around the base.

In May, US warplanes struck pro-Assad forces — including Hezbollah and Iranian-supported Iraqi militia — on three occasions when they moved inside the zone.