At least 12 pro-regime fighters were killed in an overnight Israeli strike that targeted a factory near Aleppo in the north of Syria, an NGO reported early Monday.

"Twelve pro-Iranian fighters of Syrian and foreign nationalities were killed, according to an initial tally, in an Israeli air strike on a position in the town of Hayyan, north of Aleppo, setting off strong explosions in a factory," the Syrian Observatory for Human Rights said.

The Syrian Ministry of Defence said in a statement that "after midnight... the Israeli enemy launched an air attack from the southeast of Aleppo, targeting some positions" near the city, adding that "the aggression caused several martyrs and material damage".

According to the Observatory -- which is based in Britain, but maintains a vast network of sources inside Syria -- rescuers and firefighters were deployed to the site to treat the injured and contain blazes caused by the strike.

The NGO said that Hayyan is "controlled by pro-Iranian groups composed of Syrians and foreigners".

Israel has carried out hundreds of strikes on its northern neighbour since the outbreak of Syria's civil war, mainly targeting army positions and Iran-backed fighters, including from the militant group Hezbollah.

While it rarely comments on individual strikes in Syria, Israel has repeatedly said it will not allow its arch-enemy Iran to expand its presence there.

The strikes have increased since its war with Hamas in the Gaza Strip began on October 7, when the Iran-backed Palestinian militant group launched an unprecedented attack against Israel.

Syria's war has killed more than half a million people and displaced millions more since it erupted in 2011 after Damascus cracked down on anti-government protests.