Al-Sharaa denounced the bombing as a "despicable crime" that targeted innocent worshippers at the Mar Elias Greek Orthodox Church in the al-Dula district of Damascus.
"This horrific act has shaken the conscience of the entire nation," he said, extending condolences to the families of the victims.
At least 25 people were killed and 63 injured in Sunday's explosion, according to the Interior Ministry.
Officials have blamed the Islamic State group for the attack, raising alarms over the group's lingering threat in the country.
Al-Sharaa urged Syrians to rally together, stressing the importance of solidarity in the face of terrorism.
"This heinous act reminds us of the urgent need for unity - between the government and the people - to confront anything that threatens our country's security and stability," he said.
Although Islamic State was declared militarily defeated in Syria in 2019, its sleeper cells continue to launch sporadic attacks, exploiting security gaps in the war-torn country.
Concerns over a potential resurgence have intensified since the toppling of long-time ruler Bashar al-Assad in December.
The attack has also renewed fears for Syria's religious minorities, particularly Christians, amid a fragile political transition.
The current interim government, dominated by the jihadist group Hayat Tahrir al-Sham, faces growing scrutiny from both domestic and international observers regarding the protection of minority rights.
With the majority of Syrians identifying as Sunni Muslims, calls are mounting for the transitional leadership to ensure inclusive governance and security for all communities.
Syria's Interior Ministry announced on Monday that security units, in co-ordination with the General Intelligence Service, have made significant progress in identifying and dismantling the responsible terrorist network.
"Following the treacherous terrorist attack, our security forces intensified their efforts - gathering intelligence, analysing evidence and establishing a joint operations room with the General Intelligence Service to cross-check and verify information," a statement read.
According to the ministry, this collaborative work led to a series of precision operations targeting terrorist cells linked to Islamic State in the outskirts of the capital, specifically in the towns of Harasta and Kafr Batna, near Damascus.
"These operations led to armed clashes, resulting in the arrest of the cell leader and five of his associates. Two other terrorists were killed during the raids - one of whom had facilitated the suicide bomber's entry into the church, and another who was preparing for a separate attack in a different Damascus neighbourhood," the statement said.
Authorities also seized a cache of weapons, ammunition, explosive vests and mines.
Notably, a motorcycle rigged with explosives and intended for detonation was discovered and safely neutralised.
"The Interior Ministry affirms that these cowardly terrorist acts will only strengthen our resolve. We will relentlessly pursue all those who attempt to undermine the nation's security," the ministry concluded.
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