Nairobi/Mogadishu - A moderate Somali Islamist group on Thursday seized control of a second town from main insurgent group al-Shabaab as the groups battle to fill gaps left by the departure of Ethiopian troops.

The fighting came as internationally backed plans to form a unity government and elect a new president gathered pace.

The government-aligned Ahlu Sunnah Waljamaca attacked the central town of Dhusamareb in the morning, Somali news portal Mareeg. com reported.

At least five people were killed and 20 injured in the fighting, which also caused hundreds of residents to flee.

Al-Shabaab, which has been waging a bloody insurgency since early 2007, on Monday took over Baidoa, the seat of the Somali parliament, just hours after Ethiopian troops who had been propping up the central government for two years left.

The group controls large swathes of Somalia and is pushing to seize complete control of southern and central Somalia.

However, it has faced fierce opposition from Ahlu Sunnah Waljamaca, which accuses al-Shabaab of killing civilians and desecrating graves.

The moderate group has already taken over the town of Guriel from al-Shabaab, which the US says has links to al-Qaeda.

Despite the fighting, political moves are still ongoing to create a larger national parliament and elect a new president.

Somali MPs, meeting in neighbouring Djibouti on Monday, voted to double the number of seats in parliament from 275.

Many of the 200 new MPs from moderate opposition group the Alliance for the Re-Liberation of Somalia (ARS) were sworn in on Wednesday, with the rest expected to follow suit on Thursday.

Another 75 seats have been set aside to be allocated to members of civil society and other opposition parties at a later date.

The MPs are also expected to appoint a new president on Friday.

ARS leader Sheikh Sharif Sheikh Ahmed is running, along with current Prime Minister Nur Hassan Hussein.

President Abdullahi Yusuf Ahmed resigned in December after parliament thwarted his attempt to sack Hussein.

The United Nations is hoping that the creation of a unity government will help bring an end to the chaos that has plagued Somalia since the 1991 ouster of dictator Mohamed Siad Barre.

The UN Special Representative for Somalia, Ahmedou Ould-Abdallah, said the bigger parliament was an important step to stability.

"We are finally seeing progress from the hard work by all sides to create an inclusive parliament," he said in a statement Thursday. "I would like to congratulate and encourage all the parliamentarians to work for the good of the country."

Despite the advances in creating an inclusive government, the future of Somalia remains uncertain as al-Shabaab has vowed to continue fighting to ensure that strict Islamic law is imposed in all of Somalia.

The insurgents have already installed sharia law in many towns and have not been slow to enforce it, whipping people for dancing and singing and also executing a teenage girl, who aid agencies say was raped, for adultery.

With the departure of Ethiopia, only an undermanned African Union (AU) force of around 3,000 troops from Uganda and Burundi remains to back government forces, although the two countries have put two extra battalions on standby.

The AU is trying to scrape up more troops, but the United Nations has ruled out sending in a peacekeeping force.

Ethiopian forces invaded in late 2006 to help kick out the Islamic Courts' Union, a hardline Islamist regime that was in power for six months.

The invasion sparked a bloody insurgency that has killed an estimated 16,000 civilians and displaced around 1 million.

The conflict, combined with drought and rising food prices, has created a humanitarian catastrophe. Some 3.25 million people in Somalia, almost half the population, are dependent on food aid. (dpa)