The World Council of Churches (WCC) has urged Armenia and Azerbaijan to obey a ceasefire order after recent violence between the two nations has led to at least 600 deaths.
The countries are fighting over the separatist territory of Nagorno-Karabakh.
Nagorno-Karabakh military officials said 16 more of their servicemen had been killed in fighting on Tuesday, bringing total number of dead among military members to 532 since 27th September, when the fighting started.
Azerbaijan has not disclosed its military losses, and the overall toll is likely to be much higher with both sides regularly claiming to have inflicted significant military casualties on one another.
Azerbaijani authorities said 42 civilians have been killed on their side in over two weeks. Nagorno-Karabakh human rights ombudsman Artak Beglaryan reported at least 31 civilian deaths in the breakaway region late on Monday. Hundreds more have been wounded.
WCC, which represents more than 500 million Christians worldwide, is deeply concerned.
It said in a statement: "We urge all parties to the conflict to end all military actions immediately, to respect the ceasefire agreement reached in Moscow, and to engage in constructive dialogue aimed at protecting human lives and rights, preventing attacks on civilian infrastructure and places of worship, and achieving a sustainable peace.
"Among many other tragic impacts of the conflict already, we were shocked and dismayed by the attack on the Ghazanchetsots cathedral (pictured above), in which civilians were sheltering at the time. We condemn any targeted attack on one another's religious and cultural sites."
The recent fighting between Armenian and Azerbaijani forces broke out on 27th September. More than two weeks of deadly clashes marked the biggest escalation of a decades-old conflict over Nagorno-Karabakh, which lies in Azerbaijan but has been under control of ethnic Armenian forces backed by Armenia since the end of a separatist war in 1994.
Both sides have repeatedly accused each other of attacks amid appeals from around the globe to end the hostilities and start peace talks.
Armenian and Azerbaijani foreign ministers signed a ceasefire deal last week. The truce that took effect on Saturday was brokered by Russia, which has a security pact with Armenia. But Moscow has also cultivated warm ties with Azerbaijan and seeks to mediate in the conflict.
The truce, however, has been immediately challenged with both Armenia and Azerbaijan accusing each other of continued attacks in violation of the agreement.
On Tuesday, Azerbaijani officials have once again accused Armenian forces of shelling some of its regions, and Nagorno-Karabakh officials said Azerbaijan launched "large-scale military operations" along the front line.
Russia and the European Union have urged both sides to observe the ceasefire.
WCC added: "We pray and hope that religious leaders and institutions, together with decision makers, can join together in concerted efforts for an end to this conflict, for the protection of every human life, for the promotion of interreligious understanding and respect for each others' communities and holy places, and in cooperation for peace, justice and human dignity."
The Conference of European Churches (CEC) has also spoken out against the violence.
CEC President Rev Christian Krieger further stressed the need for reconciliation between all parties. He said: "Nothing can justify an attack on churches and the civilian casualties. Attacks on religious heritage hurt religious sentiment and may add a religious dimension to an otherwise complex conflict."
CEC has been engaging in advocacy work with international organisations, calling on OSCE Minsk Group and the European External Action Service (EEAS) to increase their efforts in searching for a durable peaceful solution in the Nagorno-Karabakh region.
CEC general secretary Dr Jørgen Skov Sørensen in his letters to EEAS and OSCE, stressed the need for the "inclusion of religious leaders in the negotiation process from both sides to help the reconciliation process between the two neighbours."