Forensic experts quickly rushed to the scene to establish how the attack which cost one person's life took place .
The victim, who attended the celebration, first identified by his initials C. T., was called Tuncer Cihan, Interior Minister Ali Yerlikaya said on Sunday evening.
The two attackers were arrested as they tried to flee, the government announced.
In footage taken by security cameras before the attack, two men can be seen wearing black masks and with their hands in their pockets . One of them has sunglasses.
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The attack occurred around 11:40 a.m. local time. About 40 people attended the mass, according to local officials, including the Polish consul general in Istanbul, Witold Lesniak, and his family.
< p class="Text-sc-2357a233-1 imohSo">After the second shot, the firearm no longer worked, so the attackers fled. At this time, everyone was lying on the ground. There were between 35 and 40 people inside.
A quote from Sukru Genc, neighborhood mayor
L' The attack left no one injured, according to Istanbul Governor Davut Gul.
Turkish President Recep Tayyip Erdogan assured earlier that the necessary measures had been taken to arrest the attackers, whose motive remained unknown.
Pope Francis expressed from Rome his closeness to the community of this church. We strongly condemn this despicable attack, he added.
The Italian Foreign Minister also expressed his condolences and strong condemnation.
The attack comes more than a week after a meeting in Istanbul between Mr. Erdogan and Italian Prime Minister Giorgia Meloni.
Several were in a state of shock after the attack, although no injuries were reported.
Our security forces are conducting a full-scale investigation into the case, said Omer Celik, spokesman for the ruling AKP (Justice and Development Party). Those who threaten the peace and security of our citizens will never achieve their goals.
The city's popular mayor, Ekrem Imamoglu, As for him, he said: We will never welcome into our city those who target our unity and our peace by attacking places of worship.
En December, Turkish security forces arrested 32 suspects, alleged members of the Islamic State jihadist group, suspected of planning attacks against synagogues, churches and the Iraqi embassy. The arrests were made in nine different cities, including Istanbul and the capital Ankara.
IS claimed responsibility for a number of ;deadly attacks in Turkey, including one on January 1, 2017 in a nightclub in Istanbul, which left 39 dead.