Brigadier General Ismail Qaani for the Iran Guard condemned Israel's actions.
Their support comes during the heaviest fighting between Israel and Hamas.
Iran's Revolutionary Guards Quds Force commander stressed Tehran's support for Palestinians facing Israeli "crimes" in Jerusalem and Gaza in phone calls with Islamist factions' officials, state media reported on Sunday.
The calls comes during the heaviest fighting since 2014 between Israel and Islamist group Hamas, which has claimed 181 lives in the crowded coastal enclave of Gaza and killed 10 people in Israel since Monday.
Brigadier General Ismail Qaani talked to the head of Hamas' political bureau, Ismail Haniyeh, and the secretary-general of the Islamic Jihad group, Ziyad al-Nakhalah, said state new agency IRNA.