TEL AVIV: Iranian missiles struck major Israeli cities on Monday (Jun 16) 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.

After four days of conflict between the regional foes, Iran said its parliament was preparing a Bill to leave the nuclear Non-Proliferation Treaty (NPT), adding that Tehran remained opposed to developing weapons of mass destruction.

Passing the Bill could take several weeks, but the move risks stoking deeper concerns about Iran's nuclear programme in Western countries, which have long suspected Tehran wants to build nuclear weapons, a charge Iran denies.

"Government has to enforce parliament Bills but such a proposal is just being prepared and we will coordinate in the later stages with parliament," said foreign ministry spokesperson Esmaeil Baghaei, when asked at a press conference about Tehran potentially leaving the NPT.

Israel, which said its military campaign will escalate in the coming days, began bombing Iran on Friday, saying Tehran was on the verge of building a nuclear bomb and targeting the nuclear and ballistic missile programmes.

"We are on our way to achieving our two main objectives: eliminating the nuclear threat and eliminating the missile threat," Israeli Prime Minister Benjamin Netanyahu said in comments to soldiers at the Tel Nof airbase.

Iran has always said its nuclear programme is peaceful, although the United Nations nuclear watchdog the IAEA declared last week that Tehran was in violation of its NPT obligations.

Israel is presumed to have a sizable nuclear arsenal but neither confirms nor denies it. It is the only Middle East state that has not signed the NPT.

Before dawn on Monday, Iranian missiles struck Israel's Tel Aviv and the port city of Haifa, killing at least eight people and destroying homes, prompting Israel's defence minister to warn that Tehran residents would "pay the price and soon".

Israeli authorities said a total of seven missiles fired overnight had landed in Israel. At least 100 people were wounded in Israel.