Thousands of Lebanese on Friday mourned a slain Christian political official authorities said was killed by a Syrian gang, with supporters pointing the finger at Lebanon's powerful Hezbollah group.

Pascal Sleiman was a coordinator in the Byblos (Jbeil) area north of Beirut for the Lebanese Forces (LF) Christian party, which opposes the government in neighbouring Syria and its Lebanese ally Hezbollah.

On Monday, the army said that Sleiman, who had gone missing the day before, was killed in a carjacking by Syrian gang members who then took his body across the border.

His party said it would consider Sleiman's death a "political assassination until proven otherwise".

Hezbollah chief Hassan Nasrallah has denied that his party was involved.

Speaking after Sleiman's funeral, LF leader Samir Geagea called for the "failed, corrupt" authorities in Lebanon to be changed.

Geagea blamed their failure, among other things, on "illegal weapons" -- a barely veiled reference to Hezbollah.

The Iran-backed group is the only party in Lebanon that has kept its weapons arsenal after the end of the 1975-1990 civil war, and it wields great influence on the country's political life.

Since the Israel-Hamas war broke out on October 7, Hezbollah has traded near-daily cross-border fire with Israeli forces in actions opposed by the LF and other parties.

"We don't want to wake up one day, as we did now, and find ourselves involved in a never-ending war," Geagea said Friday.

Maronite Patriarch Beshara Rai, spiritual leader of Lebanon's largest Christian sect, held back tears as he presided over Sleiman's funeral in Byblos.

Outside the St George church, LF supporters waved the party's white flag with its cedar tree -- the symbol of Lebanon -- circled in red.

Mourners told AFP they were unconvinced by the army's version that car thieves killed Sleiman.

"This story never convinced me. It is not coherent at all," said Jean Habshi, 50, who came to pay his respects.

"Enough with Hezbollah, enough with the illegal weapons," Roba Hajal, 24, told AFP outside the church.

"If they (Hezbollah) did not kill him, at the very least they allowed the Syrians in. We are all at risk of meeting Pascal's fate," she said.

Lebanon has a long history of political assassinations that have taken place with impunity.

Years of economic meltdown have further strained a weak judiciary that has been widely accused of succumbing to political interference.

Ziad Hawat, an LF lawmaker from Byblos, on Friday, called for a "serious, transparent" probe into Sleiman's murder, adding that the party had concerns "based on past experiences".

"We do not want the killer to be known to all," he added, while "remaining unknown to the judiciary".

On Tuesday, Interior Minister Bassam Mawlawi vowed to get tough on Syrians after several were arrested on suspicion of involvement in Sleiman's killing.