Islamic State militants have reportedly blown up a fourth-century monastery near Qaraqosh, according to pictures posted by the terrorist group on Twitter.

The photos show the tomb complex of Mar Behnam and Mart Sarah monastery reduced to rubble by the blast. Local Kurdish media later confirmed the explosion.

The monastery was built by the Assyrian King Senchareb about 1,600 years ago, although substantial changes were made to the building in the 14th century. It originally belonged to the Syriac Orthodox Church, but came under the Syriac Catholic Church in the 19th century.

Patriarch Ignatius Joseph III Yonan, the leader of the Syriac Catholic Church, said: "We are very very saddened to see this kind of destruction and violent turmoil."

The monastery was captured by the militants last July, shortly before the town of Qaraqosh – the largest Christian town in Iraq – was overtaken in August.

The three monks who were living there at the time were forced to flee, taking nothing with them, Yonan said, speaking from Beirut, Lebanon.

He described the monastery as "a beacon of spirituality". "It used to be a kind of oasis for the Nineveh villages during spring and summer," he said.

The monastery was also known for its carvings, and Yonan said there were still some important manuscripts kept there.

Diana Yaqco, of A Demand For Action, which campaigns for the rights of minority groups in Iraq and Syria, said: "We are very saddened but not surprised by yet another attack on our cultural and religious identity by IS, the terror and the barbarism of IS has become like a record being played over and over again with same result.

"This piece of history cannot be recreated. IS not only despises our religious beliefs but our literature, arts, and history which is irreplaceable and one of a kind."

Earlier this week IS released photos depicting the desecration of St George's church in Mosul, which allegedly took place on March 7. Militants were shown replacing the cross on the top of the church with the black IS flag.

Since February IS has attacked numerous sites of historical significance in Iraq, as well as destroying many of the artefacts in the museum of Mosul, in Syria.

"We call onto the responsible organisations to put an end to this," Yaqco said. "Or as a people we will be wiped out completely along with our churches, buildings and history all together. We will become rubble and dust and make no mistake the world leaders and international community will be judged for watching it all happen right before their eyes."

Patriarch Yonan said that he blamed Western governments, particularly the US, Britain and France, for failing to stop the growth of extremist groups such as Islamic State.

"They knew already a long time ago [about] these fanatics, [and] that they did not believe in any religious freedom, in any democratic system, but to kill in the name of Allah.

"Since the beginning of the Syrian crisis, they kept telling us that the regime will fall very soon, that Assad will go... Already [it's been] four years, and the ones who paid the price are innocent people. Iraq was the same thing.

"We beg the Christians in the West to stand up for the principle of true religious freedom and true democracy, not only numerical democracy, or voting democracy, they have to work on building a civilised system of governing."