At least three rockets struck Baghdad's fortified Green Zone near the United States Embassy late Tuesday, the fourth such attack in the span of a week.

It came a day after an attack on a training base south of the capital, where US-led coalition troops and NATO trainers were present, Iraqi security officials said.

At least three rockets struck the Green Zone, the seat of Iraq's government and home to several foreign embassies, two Iraqi security officials said.

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Myles Caggins, a spokesman for the US-led coalition, said the rockets fell at least 2km (1.2 miles) from the embassy. There were no immediate reports of casualties.

The previous evening, rockets hit the Basmaya base near the Iraqi capital, an Iraqi army statement said. The projectiles landed in an area that includes agricultural land and a factory, according to the statement. No more details were provided.

A Spanish contingent of the coalition and NATO trainers are present at the Basmaya site. There was no immediate confirmation of the attack from the coalition, and no armed group claimed responsibility.

Camp Taji

Last Wednesday, a barrage of two dozen rockets struck Camp Taji, north of Baghdad, killing three coalition servicemen, including two Americans. A British serviceman was also killed.

It was the deadliest raid to target US troops in Iraq since a late December rocket attack on an Iraqi base, which killed a US contractor and set in motion a series of attacks that brought Iraq to the brink of war.

Wednesday's barrage was followed by another raid, on Saturday at the same site, which wounded five soldiers - three coalition members and two Iraqi soldiers.

The first attack 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 for the attack.

However, Iraq's military said those air strikes killed five security force members and a civilian, while wounding five fighters from the Popular Mobilisation Forces, an umbrella organisation including an array of militias, including some Iran-backed groups.

Iran-backed Shia militia groups vowed to exact revenge, signalling another cycle of tit-for-tat violence between Washington and Tehran that could play out in Iraq.