JERUSALEM — Israel has concluded that Hezbollah's top military commander was killed in Syria last year by rivals within the Shiite militant group, Israel's military chief said Tuesday.

The explosive announcement was the latest sign of an escalating feud between Israel and Hezbollah, an Iranian-backed group sworn to Israel's destruction.

Israel considers Hezbollah to be a potent enemy, with more than 100,000 rockets and missiles aimed at the Jewish state. But it also believes the group has been weakened and demoralized after years of fighting alongside President Bashar Assad's forces in Syria.

Israel's military chief, Lt. Gen. Gadi Eisenkot, told an academic conference on Tuesday that the death of Mustafa Badreddine last May illustrated "the depth of the internal crisis within Hezbollah."

He also said it reflected "the extent of the cruelty, complexity and tension between Hezbollah and its patron Iran."

An Israeli military official said Israel believes the order to kill Badreddine was given by Hezbollah's leader, Hassan Nasrallah.

Israeli intelligence believes Badreddine had been feuding with Iranian military commanders in Syria over the heavy losses his group had suffered on the battlefield. Both Iran and Hezbollah are backing Syrian government forces.

The official spoke on condition of anonymity because he was discussing a confidential intelligence assessment.

Hezbollah had no immediate comment.

At the time of his death last year, Hezbollah said Badreddine had been killed by insurgent shelling in Syria. He was considered Hezbollah's top military official and was among five members on trial in absentia at a court in the Netherlands over the bombing that killed former Lebanese Prime Minister Rafik Hariri and 21 others in Beirut in 2005.

Badreddine was a student of Imad Mughniyeh, Hezbollah's previous military chief, who was considered one of the world's most-wanted terrorists by Israel and the United States. Mughniyeh, who was Badreddine's brother-in-law, was killed in a 2008 car bombing in Damascus that Hezbollah blamed on Israel.

Israel and Hezbollah fought a monthlong war in 2006 that ended in a stalemate. Israeli officials say that Hezbollah is far stronger than it was back then and is battle-tested after years of fighting in neighboring Syria. They frequently warn that it is only a matter of time before another war breaks out.

But Israeli officials also say the group does not want a confrontation with Israel right now. Hezbollah has gotten bogged down in the Syrian fighting and is believed to have lost hundreds of fighters.

Israel is not actively involved in the Syrian fighting. But it keeps close tabs on the battlefield actions of its enemies, Iran and Hezbollah. Israel is believed to have carried out numerous airstrikes in Syria aimed at suspected weapons shipments destined for Hezbollah.

On Tuesday, the Israeli military confirmed that a "Skylark" surveillance drone crashed in Syria earlier this week. It gave no cause for the crash and said the incident was being investigated, but said there was "no risk of a breach of information."

Hezbollah's media arm published photographs of what it said was a drone it had shot down in Syrian airspace in the Golan Heights.

Last week, Israel shot down a Syrian anti-aircraft missile fired at an Israeli aircraft carrying out an airstrike on a suspected Hezbollah weapons convoy in Syria.

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