Gunmen detonated explosives inside an Orthodox Assyrian church on Monday, setting fire to ancient icons and reducing much of its contents to ashes.

A spokesman for the Assyrian Monitor for Human Rights (AMHR), which on Monday posted photos of the destruction on Facebook, told ARA News: "Anonymous gunmen stormed the St. Charnel Church for Assyrian Orthodoxes in the Watwatiyah district of Qamishli in the midnight on Monday, and destroyed its contents."

The church is located about 13km north-east of the city of Qamishli, which is close to the Turkish border.

Photos showed a damaged painting, and damage to the walls of the church caused by fire.

Eye witness Gabi Gawriya told the ARA that several explosions were heard coming from inside the church during the raid.

"We saw a huge fire and security forces arrived and extinguished the fire. But the church was completely destroyed, you can see only ashes here," she said.

According to AMHR, the attackers stole donation boxes from the church before detonating their explosives.

It's not the first time Qamishli has been subject to a militant attack. Islamic State claimed responsibility for three terror attacks on the city in December that killed more than a dozen people.

Last month, a suicide bomber killed three people in an attack near a church that was believed to have targeted the head of the Syriac Orthodox Church.