Powerful Iraqi and Yemeni armed groups aligned with Iran have threatened to target U.S. interests with missiles and drones if Washington intervenes to support Israel in its conflict with Hamas in Gaza that already shows signs of expanding to further fronts.

The comments come amid strong support by the United States for Israel's response to the attacks and a U.S. pledge to rapidly provide additional munitions to Israel and deploy a carrier strike group to the Eastern Mediterranean.

In Iraq, Kataib Hezbollah, a powerful armed faction with close ties to Iran, said it would target U.S. bases with missiles, drones and its special forces if Washington intervened in the conflict.

U.S. officials have accused the group of previous attacks on U.S interests in Iraq. The group has denied the claims.

The United States currently has 2,500 troops in Iraq - and an additional 900 in neighbouring Syria - on a mission to advise and **** ist local forces in combating Islamic State, which in 2014 seized swathes of territory in both countries.

Iraqi politician Hadi Al-Amiri, leader of political and military group the Badr Organization that is close to Iran, had made similar threats on Monday.

"If they intervene, we would intervene ... we will consider all American targets legitimate," Al-Amiri said on Monday.

Badr comprises a large part of Iraq's Popular Mobilisation Forces (PMF), the state paramilitary organisation that contains many Iran-backed factions.

The PMF has voiced its "unequivocal support" for the Palestinian factions fighting Israel and the Iraqi government has said the Palestinian operations were a natural outcome of what it calls "oppressive" policies by Israel.

In past years, Iranian-backed militias in Iraq regularly targeted U.S. forces in Iraq and the U.S. embassy in Baghdad with rockets, though such attacks have abated under a truce in place since last year, as Iraq enjoys a period of relative calm.

'AXIS OF RESISTANCE'

In Yemen, the leader of the powerful Houthi Movement warned on Tuesday that the group would respond to any U.S. intervention in Gaza with drones, missiles and other military options.

He said the group was ready to coordinate intervention with other members of the so-called "Axis of Resistance" which encompasses Iranian-backed Shi'ite Muslim factions in Iraq and Lebanon's Hezbollah group, which has already entered the fray.

Yemen's Houthi movement has battled a Saudi-led coalition since 2015 in a conflict that has killed hundreds of thousands, during which it has targeted strategic **** ets in the Gulf, most notably energy facilities in Saudi Arabia.

Yemen has enjoyed a year of relative calm as peace negotiations gain traction.