Transport trucks carrying armoured vehicles and military trucks left the Japanese military base in southern Iraq on Friday as Japan pushed ahead with its promised troop pullout.

Prime Minister Junichiro Koizumi announced earlier this month that Japan would withdraw its roughly 550 soldiers, engaged in reconstruction and humanitarian work, from their base in Samawa in the southern province of Muthanna.

Reuters journalists saw some 20 transporters leave the base carrying jeeps, armoured personnel carriers and other vehicles.

"There is a transition going on. We are in the process of moving out of Muthanna and there is some logistics involved in the process," a spokesman for the British military in Basra said.

Iraqi Prime Minister Nuri al-Maliki said this month his forces would take over security from July in Muthanna, where the British oversee a multinational contingent that includes Japanese and Australian troops.

The pullout of the troops ends the Japanese military's riskiest and most ambitious overseas mission since World War Two. No Japanese soldiers have been killed or wounded in Iraq.

Japan has said its withdrawal from Samawa would be coordinated with Britain and Australia, whose troops provide security for the Japanese soldiers.