Tehran (AFP) - Islamic State group jihadists have killed a senior commander in Iran's Revolutionary Guards in Syria, the elite branch of the Iranian military said Friday.

General Hossein Hamedani was killed on Thursday by IS "during an advisory mission" in the northern region of Aleppo, a Guards statement said.

Hamedani had been playing an "important role... reinforcing the front of Islamic resistance against the terrorists", it added.

Ali Shamkhani, secretary of Iran's Supreme National Security Council, described Hamedani's death as "a huge loss" in the fight against jihadist groups in Syria.

Quoted by the IRNA news agency, he said the loss would be "avenged" and that this would lead to the "complete destruction" of these groups.

Shiite-dominated Iran is a staunch ally of President Bashar al-Assad, sending Guards forces and military advisers to aid him against Sunni Muslim rebels seeking his overthrow.

Lebanon's Shiite militia Hezbollah has done much of the fighting to prop up the Syrian army, though the commander of the Revolutionary Guards' foreign wing, Qassem Soleimani, is said to be heavily involved in guiding military strategy.