US forces in Iraq and Syria faced two separate rocket and explosive drone attacks in less than 24 hours, Iraqi security sources and US officials told Reuters on Monday, the first reported after a near three-month pause.

At least one armed drone was launched at the Ain al-Asad air base that hosts US troops in the western Iraqi province of Anbar, a US official said.

That followed five rockets fired from northern Iraq towards US forces at a base in Rumalyn in remote northeastern Syria, on Sunday, according to US and Iraqi officials.

There were no reports of casualties or significant damage from the drone attacks.

On Saturday, a massive explosion at a military base in Iraq killed a member of the pro-Iran Hashd al-Shaabi armed militia group. The force commander said it was an attack while the army said it was investigating and that there were no warplanes in the sky at the time. The US military denied involvement.

Near-daily rocket and drone strikes on US forces began in mid-October and were claimed by a group of Iran-backed Shiite Muslim armed groups known as the Islamic Resistance in Iraq, who cited US backing for Israel's war in Gaza.

The attacks stopped in late January under pressure from Iraqi authorities and Iran, following deadly US retaliatory airstrikes in Iraq, after three US soldiers were killed in a drone strike on a small base on the Iraqi-Jordanian border.

Iraqi Prime Minister Mohammed Shia al-Sudani returned at the weekend from a week-long visit to the United States where he met President Joe Biden in an effort to turn a new page in US-Iraqi relations despite soaring regional tensions.

The US invaded Iraq in 2003 and toppled strongman leader Saddam Hussein, withdrawing in 2011 before returning in 2014 at the head of an international military coalition at the Baghdad government's request to help fight Islamic State insurgents.

The US has some 2,500 troops in Iraq and 900 in eastern Syria on an advise-and-assist mission.

(Report by Reuters)