As violence spread to hitherto quiet areas of Iraq, gunmen kidnapped three Japanese civilians, including a woman aid worker, and threatened to kill them unless Tokyo pulled out its troops from Iraq. Eight South Korean civilians were also kidnapped.

According to agencies, a hitherto unknown group, 'Mujahideen Squadrons', gave Tokyo three days to declare a pullout, failing which the three Japanese -- two journalists and the aid worker -- would be executed.

Japan -- which has pledged 1100 soldiers on a non-combat mission to help rebuild Iraq -- has declared that it has "no reason" to withdraw. This is Japan's first deployment of troops since World War II.

South Korean new agency Yonhap said the eight South Koreans were Christian missionaries who were apprehended by "armed men," but one was later released.

Seoul has pledged 3,600 soldiers to maintain peace in the northern regions of Iraq later this year, while over 400 doctors and engineers have been sent already to the region.

In other developments, loyalists of the radical Shia cleric, Muqtada al-Sadr took over three southern cities, Kut, Najaf and Kufa, but coalition forces said they would soon regain control.

A military spokesman indicated that the presence of thousands of Shia  pilgrims gathering in Najaf for a religious festival was posing a challenge to the coalition forces, who did not want to attack innocent civilians.

Elsewhere, a US marine was killed in the strike against Fallujah, where coalition forces are engaged in pitched battles against Sunni radicals opposed to the US presence in Iraq.