Iran's military responded with a wave of missile strikes against Israel, which have killed at least 13 people as of Sunday.

The death toll is growing as Israel and Iran exchanged missile attacks for a third consecutive day on Sunday, and Israel is warning that worse is to come.

Israel unleashed airstrikes across Iran for a third day Sunday and threatened even greater force as some Iranian missiles evaded Israeli air defenses to strike buildings in the heart of the country.

An Iranian missile barrage overnight triggered a partial shutdown of a Haifa oil refinery in Israel as the two countries took turns striking at each other’s energy facilities over the weekend.

Israel said hundreds of airstrikes over the past two days killed nine senior scientists and experts involved in Iran’s nuclear program, in addition to several top generals.

“Have the Iranians killed an American yet? No. Until they do we’re not even talking about going after the political leadership," said one of the sources, a senior U.S. administration official.