No one immediately claimed responsibility for what appeared to be the deadliest militant attack to target Iran since its 1979 Islamic Revolution. Last week, a suspected Israeli strike killed a Revolutionary Guard commander in Syria. Some Iranian officials also hinted at Israeli and American involvement without offering evidence, which is common after militant attacks. Until Wednesday, the deadliest attack to strike Iran since the revolution was the 1981 truck bombing of the Islamic Republican Party’s headquarters in Tehran. That attack killed at least 72 people, including the party’s leader, four government ministers, eight deputy ministers and 23 parliament members.