Lebanon's Hezbollah denounced what the group said was Israel's deadly attack on a Gaza hospital and called for "a day of unprecedented anger" on Wednesday, as protests erupted outside the U.S. embassy in Beirut just hours after the incident.

Iran-backed Hezbollah, which fought a war with Israel in 2006, made the call for the day pf protest in Beirut in a statement late Tuesday, after Palestinian officials said hundreds of people died in the strike on the hospital.

Israel's military denied responsibility for the bombing, saying military intelligence suggested the hospital was hit by a failed rocket launch by the enclave's Palestinian Islamic Jihad terrorist group.

Islamic Jihad denied that any of its rockets were involved in the hospital blast.

Hundreds of Lebanese protesters, some waving Palestinian flags, gathered late into Tuesday night outside the U.S. embassy in response to the incident. Others gathered outside the French embassy in Beirut.

Tear gas was fired at protesters near the U.S. embassy in Lebanon.

In denouncing what the group said was a strike by Israel, Hezbollah said in its statement: "The attack reveals the true criminal face of this entity and its sponsor ... the United States, which bears direct and complete responsibility for this massacre."