Nairobi, Mogadishu  - The United Nations Special Representative for Somalia Ahmedou Ould-Abdallah on Saturday condemned the killing of civilians, as Islamic insurgents seized a major town after a bloody battle.

Over 50 died, hundreds were injured and thousands forced to flee as Islamic insurgent group al-Shabaab seized control of the strategic port of Kismayo, which lies around
500 kilometres south of Mogadishu.

Al-Shabaab took over the city on Friday after three days of bloody battles with local clan militia that saw businesses shut down and bodies littering the street.

"The Islamic Courts and al-Shabaab control Kismayo," clan elder Abdi Bashi told Mogadishu-based Radio Garowe.

The transitional federal government and moderate opposition leaders signed a ceasefire in Djibouti, but al-Shabaab, the armed wing of the Union of Islamic Courts (UIC), has rejected the truce.

Al-Shabaab and other hardliners want Ethiopian troops propping up the government to leave before beginning talks.

Violence has not abated since the ceasefire was agreed in early June, and civilians continue to suffer.

Aid agencies estimate more than 6,000 civilians have died in the last year, most of them in the capital city Mogadishu, where clashes happen daily.

Hundreds of thousands have fled Mogadishu and aid agencies say that millions of Somalis are dependent on food aid.

Government forces backed by Ethiopian troops often exchange mortar, rocket and automatic weapon fire with insurgents in heavily populated areas.

The UN Political Office for Somalia said that "a large number of civilians were killed in what appeared to be indiscriminate attacks" on the road out of capital Mogadishu last week.

Both sides are blaming each other for the attack.

Ould-Abdallah said that the killing of civilians, not only in Kismayo but in other areas, violated international law and said those responsible would be held to account.

"I call upon all parties to the conflict in Somalia to respect international human rights and humanitarian law, and to stand by their commitments under the Djibouti agreement," Ould-Abdallah said in a statement.

Militants have been waging a guerrilla war since Ethiopian troops helped the government oust the Union of Islamic Courts (UIC) in late 2006.

Despite the government's initial success and the death of al- Shabaab leader Aden Hashi Ayro in a US airstrike in May, the insurgents appear to be gaining strength.

The interim government has been unable to achieve stability in the Horn of Africa country, which has been plagued by chaos and civil war since dictator Mohamed Siad Barre was toppled in 1991. (dpa)