BEIRUT — In a surprise announcement Saturday, Lebanon’s Hezbollah militia blamed the recent killing of a militant described as its top commander in Syria on extremist Sunni insurgents. Many had expected the powerful Shi’ite group to point a finger at its traditional nemesis, Israel.

Hezbollah revealed a day earlier that Mustafa Badreddine, one of its most senior figures, died in a mysterious blast in Damascus, the Syrian capital. Before leading thousands of militants in Syria, Badreddine, 55, is suspected of playing roles in the assassination of a Lebanese prime minister in 2005 and other bombings that date back to the attack on US Marine barracks in Beirut in 1983.

Analysts said Friday that Badreddine’s killing appeared to bear the hallmarks of an air raid by Israel, which has targeted a number of the Lebanese militants in Syria in recent years. But in a statement, Hezbollah blamed it on ‘‘artillery bombardment carried out by takfiri groups in the area.’’

Hezbollah uses takfiri, an Arabic word, to describe its extremist Sunni Muslim enemies, including Al Qaeda and the Islamic State.

Hezbollah didn’t specify which group killed Badreddine, 55, or when it happened.

The incident comes amid apparently rising fatigue experienced by Shi’ite militants in Syria aligned with President Bashar Assad that are battling his Sunni-led rebellion, analysts say. In recent weeks, scores of the militants from Iran, Iraq, and Hezbollah have been killed by hard-line Sunni groups, notably Al Qaeda-affiliated Jabhat al-Nusra.

Badreddine’s killing by hardline Sunni fighters, if confirmed, would further highlight how the Syrian civil war has become a proxy conflict driven by sectarian divisions.

Saudi Arabia, a Sunni powerhouse, plays an important role in backing the Sunni-led rebellion that is fighting Hezbollah and other pro-government Shi’ite fighters that have loyalties to Iran. The Shi’ite nation is Saudi Arabia’s primary enemy, and the two countries are locked in a region-wide competition for influence.

‘‘Things will escalate because of this,’’ said Talal Atrissi, a Lebanese analyst who is close to Hezbollah.

‘‘I expect that in retaliation for Badreddine’s killing, Hezbollah will carry out a number of special operations attacks against Jabhat al-Nusra and ISIS.’’

In recent weeks, a shaky cease-fire that took effect in February appears to have intensified battles between pro-government Shi’ite militants and hardline Sunnis, particularly Jabhat al-Nusra. The Al Qaeda affiliate is not party to the cease-fire, prompting it to carry out assaults against pro-government forces.

Last week, Jabhat al-Nusra fighters attacked a government-held area near the northern city of Aleppo, killing scores of Iranian and apparently Hezbollah fighters. A tally of media reports on the killings by the Reuters news agency put the number of dead at as high as 80.

At least 17 of the killed were Iranians, which the news agency said could have been the highest toll in a battle outside of the Islamic Republic since its war with Iraq in the 1980s.

Since the start of the Syrian conflict in 2011, dozens of Iranian militants — including generals — have been killed in Syria. Some estimates put the number of Hezbollah dead at well over 1,000. Iran and Hezbollah intervened militarily to prop up the Syrian leader, their ally.

The Assad government is dominated by members of the Alawite religious group, an offshoot of Shi’ite Islam.

It is unclear why so many of the Shi’ite militiamen have been dying in Syria recently.

Labib Kamhawi, an analyst based in Jordan, attributed the deaths to competition between Russia and Iran for influence over Assad. Last year, Moscow intervened militarily against opponents of the Syrian leader and has seen its influence in the country rise at the expense of Iran’s, Kamhawi said.

In March, Russia ordered a partial drawdown of its forces in Syria but continues to launch airstrikes at government opponents.

‘‘Russia has reduced its airstrikes in Syria, and so all those Iranians are getting killed because of a lack of air cover,’’ Kamhawi said.

‘‘This seems to be part of a Russian strategy to marginalize Iran’s role in Syria and make its influence unparalleled.’’