2 Americans killed in rocket attack on base in Iraq

Two American service members were killed in a rocket attack on military base in Iraq, U.S. officials said Thursday. A British soldier also died and 14 others were wounded, they added.

At around 7.30 p.m. local time [12.30 p.m. ET] on Wednesday around 30 rockets were fired at Camp Taji, an Iraqi base to the north of the country's capital, Baghdad, Chairman of the Joint Chiefs of Staff Gen. Mark Milley told reporters at the Pentagon on Thursday. As many as 18 hit the base, he added.

Of the 14 people wounded, five were in an "urgent" condition, Milley said, adding that the groups responsible would be held accountable.

Testifying at a House Armed Services Committee hearing earlier on Thursday, Gen. Kenneth McKenzie, head of the U.S. Central Command, said that the attack was still being investigated, but the U.S. believed Iran-backed militia groups were most likely behind the assault.

"The Iranian proxy group Kataeb Hezbollah is the only group known to have previously conducted an indirect fire attack of this scale against U.S. and coalition forces in Iraq," he said.

Kataeb Hezbollah was blamed by the U.S. for a rocket attack on the K1 base near Kirkuk in northern Iraq in late December, that killed an American contractor Nawres Hamid, 33, and set off a dangerous escalation between Iran and the United States earlier this year.

However, no group has claimed responsibility for the attack.

Secretary of Defense Mark Esper said Thursday he had spoken to President Donald Trump about the incident. Asked whether he would consider retaliatory strikes inside Iran, Esper replied that he was "not going to take any option off the table" but was focused on the groups the U.S. believed to be responsible for the attack in Iraq.

Britain's Ministry of Defense confirmed in a statement that a service member from the Royal Army Medical Corps had died in Wednesday's attack,

Camp Taji hosts personnel for training and advising missions from the U.S.-led coalition tasked with fighting the Islamic State group in Iraq and Syria.

Coalition forces said in a statement on Thursday that a barrage of 18 107mm Katyusha rockets hit the base. Iraqi security forces found a rocket-rigged truck a few miles from Camp Taji, they added.

Two U.S. officials, who spoke to NBC News on the condition of anonymity on Wednesday, said the injured military personnel or contractors were from three different nationalities and included Americans. It was not initially clear how many of those injured were members of the military.

A State Department spokesperson said Secretary of State Mike Pompeo spoke with U.K. Foreign Secretary Dominic Raab Wednesday.

"We must find those responsible. I welcome the Iraqi President's call for an immediate investigation to hold perpetrators to account - but we must see action," Raab said in a statement on Thursday.

The rocket attack in late December on a military base in Kirkuk that killed a U.S. contractor prompted American military strikes on weapon depots that Washington said were linked to the Iranian-backed militia group, Kataeb Hezbollah, whom it blamed for the initial rocket attack.

Those strikes in turn prompted protests at the U.S. embassy in Baghdad and were later followed on Jan. 3 by a U.S. airstrike that killed a top Iranian general, Qassem Soleimani and Abu Mahdi al-Muhandis, a leader of the Iran-backed militias in Iraq, of which Kataeb Hezbollah is a member.

Iran then retaliated on Jan. 8 by firing more than a dozen ballistic missiles at two Iraqi air bases housing U.S. forces.