By Alexander Cornwell, Parisa Hafezi and Jeff Mason TEL AVIV/DUBAI/WASHINGTON (Reuters) -Iranian missiles struck major Israeli cities on Monday while Israel's prime minister said his country was on its way to eliminating "threats" from nuclear and missile facilities in Iran and civilian casualties mounted on both sides.

The U.S. military is operating in the air, on land and at sea to shoot down Iranian missiles fired at Israel.

The Israel Defense Forces said alerts were activated in several areas of the country after the detection of missiles launched from Iran toward Israel. The Air Force was working to intercept them, the IDF said.

By Alexander Cornwell, Parisa Hafezi and Jeff Mason TEL AVIV/DUBAI/WASHINGTON (Reuters) -Iranian missiles struck Israel's Tel Aviv and the port city of Haifa before dawn on Monday, destroying homes and fuelling concerns among world leaders at this week's G7 meeting that the battle between the two old enemies could lead to a broader regional conflict.

A volley of missiles launched by Iran killed eight people and injured nearly 100 in Israel on Monday as the conflict between the two countries entered its fourth day.

Aerial attacks between Israel and Iran continued overnight into Monday, marking a fourth day of strikes following Israel's Friday attack. That surprise strike hit the heart of Iran's nuclear program, killing several nuclear scientists as well as high-ranking military leaders, according to Israeli officials.

The Navy is sending the USS Thomas Hudner to bolster air defense systems in the region as fighting between Israel and Iran continues.