By Abdi Guled and Abdi Sheikh

MOGADISHU, Feb 26 (Reuters) - Somalia's new prime minister returned to Mogadishu on Thursday for the first time since his appointment and called for an end to fighting that has killed more than 80 people since Tuesday.

Sporadic shooting could be heard as Omar Abdirashid Ali Sharmarke, the Western-educated son of an assassinated former president, landed in the capital.

"I am very happy to return after a decade. This is my motherland. Our main priority is providing better security," he told reporters at the city's heavily guarded airport.

"I am asking Somalis to avoid shedding any more blood."

This week's fierce artillery and machine gun battles pitted Islamist insurgents, including the hardline al Shabaab group, against government forces and a small African Union peacekeeping mission of troops from Uganda and Burundi.

More than 16,000 civilians have been killed in the two-year-old insurgency, one million people have been driven from their homes, more than a third of the population depend on aid, and large parts of Mogadishu lie empty and destroyed.

The latest violence flared just days after new President Sheikh Sharif Ahmed returned to Mogadishu to try to form an inclusive unity government -- the 15th attempt in 18 years to bring peace to the failed Horn of Africa state.

MOGADISHU MEETING PLANNED

Speaking in Brussels after a meeting of the International Contact Group -- a multi-nation group trying to broker peace in Somalia -- his new foreign minister, Mohamed Abdullahi Omaar, said the fighting should not be seen out of context.

"Any peace process is never 100 percent within five days. This government is only five days old," he told reporters.

"It's very essential that one incident in one locality ... is not put out of context ... Somalia is bigger geographically than the United Kingdom."

Omaar said the new cabinet would hold its first meeting in Mogadishu this weekend, and priorities for the first three months were to establish a base in the city, set up functioning ministries and put in place a "serious" peace process.

Al Shabaab gained support as one of many insurgent groups waging war against Ethiopian troops propping up the previous government. An Ethiopian withdrawal in January placated some Somalis, but al Shabaab has now turned its fire on the AU peacekeeping force, AMISOM, and Ahmed's fledgling government.

Aid group Medecins Sans Frontieres (MSF) said on Thursday its doctors had treated 121 people during a 24-hour period between Tuesday and Wednesday at a clinic in the capital.

It said 47 of them were women and children under 14, showing that civilians were paying a heavy price for the fighting. All their wounds were caused by explosions and fire arms, it added.

"The team worked flat out all night," Shelagh Woods, head of MSF's mission in Somalia, said in Geneva. (Additional reporting by Ibrahim Mohamed in Mogadishu, Ingrid Melander in Brussels and Stephanie Nebehay in Geneva; Writing by Daniel Wallis; Editing by Louise Ireland)

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