At least 13 military advisers attached to Iran’s Islamic Revolutionary Guard Corps were killed while fighting in the Syrian village of Khan Touman, Iranian media reported Monday.

Former IRGC Maj. Gen. Mohsen Rezaei, secretary of Iran’s Expediency Council, announced that the soldiers had been killed as ISIS forces launched a surprise attack and recaptured the village. In addition to the 13 acknowledged fatalities, 21 troops were reported injured. All the fatalities were said to be from the northern Iranian province of Mazandaran.

The attack on the town, which is south of Aleppo, left more than 70 dead on Friday, according to the UK-based Syrian Observatory for Human Rights. The Observatory’s sources said that around 30 of those killed were fighting on behalf of Syrian President Bashar al-Assad.

Some Iranian sources claim that the number of dead is higher than what authorities have acknowledged, the London-based Arab news site Asharq al-Awsat reported.

The IRGC, which reports directly to Iranian Supreme Leader Ayatollah Ali Khamenei, has suffered significant losses while fighting in support of the Assad regime in Syria. Mounting casualties, including the death of a general and two colonels, compelled the force to acknowledge its presence in Syria last October. The IRGC reportedly cut its presence in Syria by more than half in December.

Iran has bolstered its involvement in Syria by recruiting foreign Shiite fighters, sometimes coercively, from Afghanistan and Pakistan. Iran has also sent members of its regular armed forces to fight in Syria. Four such troops were reported killed in Syria last month.

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