Christians are fearing for their future in Syria after a suicide bomber killed 25 worshippers at an evening service on Sunday.
The attack happened at St Elias Greek Orthodox Church in Damascus.
Reports suggest the killer opened fire on the worshippers before setting off his suicide vest. Dozens of people were also injured in the deadly attack.
In a statement, the Antiochian Greek Orthodox Patriarchate said "the treacherous hand of evil struck" the church.
It strongly condemned the "heinous" and "horrific" attack, and demanded that the Syrian government take “full responsibility”.
It also wants to see definitive action to prevent future attacks on Christians and “violations of the sanctity of churches”.
Sources told Christian Solidarity Worldwide (CSW) that the government has beefed up security in the wake of Sunday's attack by deploying police to churches and Christian neighbourhoods in Damascus.
CSW’s CEO Scot Bower said: "We extend our sincere condolences to the families and loved ones of the victims of this heinous attack, and wish the injured a swift and full recovery.
"We also commend the government’s response and urge President Al-Sharaa to deal swiftly and decisively with sectarian incitement, ensuring that all Syrian citizens receive protection from sectarian violence and equal treatment under the law."
He called on the international community to support the Syrian people "at this critical time of transition".
"The Syrian government must be encouraged to speed up the transitional justice process and launch a national dialogue initiative to address sectarianism and divisions between different community groups without further delay," he added.
One Syrian Christian who is a local partner of Open Doors is sceptical about the rhetoric of officials. He claimed that the authorities are only “pretending to protect the rights of everybody in Syria".
"The pressure of Islamisation is around every corner in Syria," he said.
The attack has only left the country's Christian minority feeling more fearful.
"This incident will make Christians and church leaders live on their tiptoes waiting for the next attack," he continued.
"We pray that the international community and the blood of these martyrs will advocate for the rest of the Christians in Syria.”
A young Christian woman from Damascus told Open Doors, “I lost all hope that there is any life left here for us.”
Open Doors’ partner group in Syria is supporting the Greek Orthodox Church throughout the country and offering trauma counselling to those affected by the bombing.
The current Syrian government is under the domination of an Islamist group that began life as an offshoot of al-Qaeda. They were one of the key forces involved in dethroning the government of the secular ruler, Bashar al-Assad last December.
Despite its Islamist origins, the new regime has said it wishes to respect the rights of religious minorities. However, questions remain about how effective it is in reining in more extreme elements within its ranks and whether it can exert control over the many armed groups active in different parts of the country.
Syria ranks 18th in the latest Open Doors World Watch List of the worst countries for the persecution of Christians.
