Missiles hit an air base in Syria early Monday in a strike that Russia blamed on Israel, an assault that comes on the heels of an alleged chemical-weapons attack on a Damascus suburb that killed dozens of civilians and spurred calls for international action.

At least 14 military personnel were killed in the strike, including three Syrian commanders, according to the Syrian Observatory for Human Rights. Seven Iranians died in the attack and their bodies were brought back to the country, according to Iran’s semiofficial Fars...