The leader of the Lebanese group Hezbollah said Iran's missile attacks on two Iraqi bases housing US troops was just the beginning of actions that would be taken in response to the US's killing of a top Iranian general in a drone attack.

In a 90-minute speech on Sunday, Hassan Nasrallah called the attacks a "slap" to Washington, describing the attack as the "first step down a long path" that would ensure the withdrawal of US troops from the Middle East.

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"The Americans must remove their bases, soldiers, officers and ships from our region. They should leave," he said. No one died in the attacks which mainly appeared to have been a show of force.

"The alternative ... to leave vertically is leaving horizontally," Nasrallah said, apparently suggesting US troops would exit the Middle East in coffins if they did not go voluntarily.

The Hezbollah leader also called on Iran's allies to begin working to take action for the killing of Qassem Soleimani, the head of the elite Islamic Revolutionary Guard Corps' (IRGC) Quds Force.

"We are speaking about the start of a phase, about a new battle, about a new era in the region," he said.

Hezbollah is closely aligned to Iran and the IRGC provides training for Hezbollah combatants who fought in Syria.

Retaliatory measures

Nasrallah's comments came as rockets slammed into an Iraqi airbase north of Baghdad where US troops are based. Security forces said several Iraqi airmen were wounded in the attack. There was no claim of responsibility.

The speech marked one week since Soleimani was killed in a US air attack on January 3 at Baghdad's international airport.

Iraqi militia commander Abu Mahdi al-Muhandis and several others were also killed in the attack, which led to escalating US-Iran tensions, which had already been high before Soleimani's killing.

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Iran had for days promised to respond forcefully before launching the missile attacks on Wednesday. Afterwards, Foreign Minister Mohammad Javad Zarif said on Twitter the country had "concluded proportionate measures in self-defence".

Both sides have scaled down their threats since Iran admitted to killing 176 people by "unintentionally" shooting down a Ukrainian passenger plane hours after the missile attacks.

Nasrallah praised Iran's leadership for admitting it accidentally shot down the plane, calling the acknowledgement "transparency that is unparalleled in the world".

Iran initially said a technical failure caused the crash and insisted its armed forces were not to blame.