The attacks in the capital Mogadishu -- dubbed as "days of bloody clashes" -- have left at least 50 fighters dead, Somali Prime Minister Mohamed Abdullahi Mohamed said Sunday.

"Several extremist insurgents have been killed in the fighting with only five minor injuries on our own troops," the premier said.

However, some 15 civilians have also lost their lives in the attacks.

Al-Shabab accuses AU troops of invading the country. The fighters say they will continue their battles until the AU forces withdraw from Somalia.

For months, Mogadishu has been the scene of daily battles between government forces and local fighters -- both of whom are trying to take control of the capital.

Also on Sunday, at least 27 al-Shabab fighters were killed in fresh clashes with government-backed troops in the central Somali region of Hiran, Somali government spokesman Mohamed Nur Dabash told Press TV.

He added that the soldiers were now on the verge of capturing the region from the fighters.

At least 13 government soldiers lost their lives in the clashes as well.

The fresh attacks come as Burundi sent an additional battalion of 850 soldiers to Somalia to bolster the AU peacekeeping mission in the Horn of African country.

The recent deployment brings to about 8,050 the number of AU troops in Somalia.

The other major contributor of AU troops in Somalia is Uganda.

The African Union peacekeeping force in Somalia is struggling to hold back al-Shabab fighters and to keep Somalia's besieged government in power.

The latest report by the International Committee of the Red Cross (ICRC) says thousands of civilians have been injured in recent months in clashes throughout the country in the Horn of Africa.

Compared to last year, it is an increase of 25 percent in the total number of war casualties and 72 percent in the number of war-wounded women and children admitted to hospitals.

Some 4,000 patients with war injuries, among them 1,100 women and children, were taken to Mogadishu's two referral hospitals in 2009.

Somalia has not had a functioning government since 1991, when warlords overthrew former dictator Mohamed Siad Barre.

Over the past two decades, up to one million people have lost their lives in fighting between rival factions and due to famine and disease.

There are more than 1.4 million Internally Displaced People (IDPs) in Somalia. More than 300,000 IDPs are sheltered in Mogadishu alone.

Most of the displaced live in poor and degrading conditions in makeshift camps in southern and central Somalia, according to the United Nations High Commissioner for Refugees.