The U.N. humanitarian chief for Somalia says fighting for control of al-Shabab's largest remaining stronghold appears “imminent.”

In a statement Tuesday, U.N. official Mark Bowden said he is “deeply concerned” about reports of civilian casualties in Port Kismayo caused by naval gunfire and airstrikes. He called for all parties to minimize the conflict's impact on civilians.

Several African nations have troops in Somalia fighting al-Shabab, which is allied with al-Qaida.

Last Saturday, an unidentified naval ship fired shells on Kismayo, killing three people and injuring four.

A Kismayo resident told VOA on Tuesday there is no sense in the town that a major battle is about to happen.

Kismayo is al-Shabab's most strategically important stronghold. The port gives al-Shabab access to the sea. And just south of the area, al-Shabab runs training camps in a large jungle area.

African Union and Somali government troops have made major gains this year against al-Shabab, which once controlled much of southern and central Somalia. Kenyan and Ethiopian forces are also in Somalia fighting the group.

In June, Kenyan Prime Minister Raila Odinga said the Kenyan military hoped to capture Kismayo by August.