Sunni extremists were to blame for the killing of Hezbollah's high-ranking commander Mustafa Badreddine in Syria, the Lebanese Shiite group said in a statement on Saturday.
"The blast that targeted one of our positions near Damascus International Airport, leading to the martyrdom of our brother commander Sayyid Mustafa Badreddine, was caused by artillery shelling carried out by takfiri [Sunni extremist] groups positioned in the area," the statement read.
Badreddine, the third leading Hezbollah commander killed in Syria in the past two years, died in an explosion in Syria on Tuesday and was buried in Beirut's southern suburbs on Friday.
The Britain-based Syrian Observatory for Human Rights, however, cast doubts on Hezbollah's version of the events.
The Observatory said that sources in both the Syrian regime and rebel forces active in the area informed it that there had been no shelling near the airport, and its own activists did not record any shells landing there.
The Observatory added that Hezbollah should reveal the "actual truth" behind the killing of its commander. Lebanese media have speculated that Israel - which has repeatedly targeted Hezbollah forces involved in the Syrian conflict - may have been involved.
Badreddine has reportedly led Hezbollah's operations since 2011 in Syria, where the group's well-trained and battle-hardened fighters have provided key backing to President Bashar al-Assad's overstretched forces.
Badreddine and five other Hezbollah members were indicted by the UN-backed Special Tribunal for Lebanon over the 2005 assassination of former Lebanese prime minister Rafik Hariri.
Badreddine was also linked to the 1983 bombing of the US Marine barracks in Beirut that killed 241 personnel.
In 2012, the US Treasury imposed sanctions on Badreddine and other Hezbollah leaders, citing the movement's "active support" to al-Assad's regime and its role in "terrorist activities."
Hezbollah is believed to have lost more than 1,200 fighters in the Syrian conflict, which started with peaceful pro-democracy protests in March 2011.