An Iran-backed militia vowed on Monday to retaliate for US military strikes in Iraq and Syria which killed 25 of its fighters and wounded dozens. “Our battle with America and its mercenaries is now open to all possibilities,” Kataib Hizbollah said in a statement. “We have no alternative today other than confrontation and there is nothing that will prevent us from responding to this crime.” Iraq described the attacks on Kataib Hizbollah as a “flagrant violation” of its sovereignty, and Iran said the airstrikes were “an obvious case of terrorism”. Moqtada al-Sadr, the notorious Iraqi Shia cleric, said on Monday that he was willing to work with Iran-backed militia groups – his political rivals – to end the United States military presence in Iraq through political and legal means. If that does not work, he will “take other actions” in cooperation with his rivals to kick out US troops. Sadr’s militia fought US troops for years following Washington’s invasion of Iraq in 2003. Iraqi Shiite cleric and leader Moqtada al-Sadr attends a meeting with Iraqi Prime Minister in Najaf on June 23, 2018 The US launched strikes against five targets in Iraq and Syria on Sunday, aiming to damage Kataib Hizbollah – a separate entity to the better-known Hizbollah, based in Lebanon. The US blames the group for the killing last week of an American contractor in a rocket attack on an Iraqi military base. The US attack – the largest targeting an Iraqi state-sanctioned militia since 2011 – represents a new escalation in the proxy war between the US and Iran playing out in the Middle East. Russia’s foreign ministry called the “exchange of strikes” between Kataib Hizbollah and US forces in Iraq “unacceptable,” and called for restraint from both sides. “We consider such actions unacceptable and counterproductive. We call upon all parties to refrain from further actions that could sharply destabilise the military-political situation in Iraq, Syria, and the neighboring countries,” a ministry statement said. Thousands of protesters blocked roads and bridges across southern Iraq on Dec 23, condemning Iranian influence and political leaders who missed another deadline to agree on a new prime minister Benjamin Netanyahu, the Israeli prime minister, praised the “important” strikes, in a phone call to Mike Pompeo, the US secretary of state. Mr Netanyahu “congratulated him on the important US action against Iran and its proxies in the region,” according to a statement issued by the Israeli leader’s office. Mr Pompeo said the strikes send the message that the US will not tolerate actions by Iran that jeopardise American lives. “We have repeatedly – the president, the secretary of state – made clear that if we are attacked by the regime or its proxies we will respond,” said Brian Hook, Donald Trump’s special envoy to Iran. He refused to comment on further possible actions. The US has maintained some 5,000 troops in Iraq at the invitation of the Iraqi government, to help assist in the fight against the Islamic State group. But on Monday Iraq’s prime minister, Adel Abdul Mahdi, said that invitation could now be rescinded. “The prime minister described the American attack on the Iraqi armed forces as an unacceptable vicious assault that will have dangerous consequences,” his office said.