A barrage of rockets hit a base housing US and other coalition troops north of Baghdad, Iraqi security officials said on Saturday, just days after a similar attack killed three servicemen, including two Americans. At least 33 rockets hit Iraqi air defence units at the Camp Taji airbase, the country’s military said. “The initial toll is two wounded Iraqi Air Defence personnel who are in very critical condition,” said Tahsin al-Khafaji, spokesman for Iraq’s Joint Operations Command. The US-led coalition said three of its members were also wounded in the attack. The attack was unusual because it occurred during the day. Previous assaults on military bases housing US troops typically occurred overnight. Six killed after US hits Iraqi targets in retaliation for rocket attack The earlier attack against Camp Taji on Wednesday prompted American air strikes on Friday against what US officials said were mainly weapons facilities belonging to Kataib Hezbollah, the Iran-backed militia group believed to be responsible. However, Iraq’s military said those air strikes killed five security force members and a civilian. Iran-backed Shiite militia groups vowed to exact revenge for Friday’s US strikes, signalling another cycle of tit-for-tat violence between Washington and Tehran that could play out inside Iraq. Wednesday’s attack on Camp Taji was the deadliest to target US troops in Iraq since a late December rocket attack on an Iraqi base. That attack killed a US contractor and set in motion a series of attacks that brought Iraq to the brink of war. After the contractor was killed, American air strikes targeting the Kataib Hezbollah led to protests at the US embassy in Baghdad. A US drone strike in Baghdad then killed Iranian General Qassem Soleimani , a top commander responsible for expeditionary operations across the wider Mideast. Iran struck back with a ballistic missile attack on US forces in Iraq, the Islamic Republic’s most direct assault on America since the 1979 seizing of the US embassy in Tehran. The US and Iran stepped back from further attacks after the Soleimani incident. A senior US official said in late January, when US-Iran tensions had cooled, that the killing of Americans constituted a red line that could spark more violence.