Heavy fighting broke out Friday in Mogadishu as Somali government and African Union troops battled a powerful militia warlord in a bid to disarm him, security officials said, reporting a number of casualties.

Three suspected Shebab Islamic militants were executed by firing squad in Mogadishu on Sunday, Somali police said.

All three had been condemned to death for murder, police chief Abdi Mohamed told AFP, with one of the men allegedly taking part in an assault on the presidential palace last month.

Somalia's Shebab insurgents said they had assassinated a lawmaker in Mogadishu as he left prayers at a mosque on Friday, the fifth MP killed this year in a string of attacks.

"This was a legitimate target, and he was killed on the orders of Allah," Shebab spokesman  Abdiaziz Abu Musab told Agence France-Presse, adding that the al-Qaida-linked insurgents were "preparing to kill all the other MPs."

Over 350,000 people in Somalia's war-ravaged capital are in acute need of food aid as government and charities struggle to cope, the U.N. warned Saturday, with other cities also in crisis.

"The food security situation has worsened as early warnings highlight drought conditions in parts of Somalia," a report from the U.N. Office for the Coordination of Humanitarian Affairs (OCHA) said.

Two alleged members of Somalia's Shebab militia convicted of murdering a female student were executed by firing squad in the capital Mogadishu on Tuesday, an AFP reporter witnessed.

"These two defendants were found guilty of murdering student Nafiso Ahmed in April," supreme military court chief judge Liban Ali Yarow said.

Several people were killed when a powerful suicide car bomb exploded near Somalia's parliament in the capital Mogadishu on Saturday, police and witnesses said.

Al-Qaida-linked Shebab rebels claimed responsibility for the bombing, the latest in a surge of attacks in Mogadishu during Islam's holy month of Ramadan.

At least two people were killed when a bomb exploded on Monday in a busy market in Somalia's capital Mogadishu at the start of Islam’s holy month of Ramadan, police said.

"The explosive device was planted under a pile of rubbish near a police post," police officer Abdi Bare told AFP.

Al-Qaida-linked Shebab militants have warned they will step up attacks in the Somali capital Mogadishu during the holy month of Ramadan, which started on Sunday.

In an audio message released on the Shebab-controlled station Radio Andalus and also on an Islamist website, the group's commander in charge of Mogadishu operations, Sheik Ali Mohamed Hussein, said the time had come when violence will be at a peak. 

At least seven people were killed Saturday, among them a prominent Somali official, in a bomb attack by Islamist militants in the center of the capital Mogadishu, officials said.

Security sources said they believed a bomb was attached to a car being driven by Abdikafi Hilowle, a police official and former secretary for the city's administration, and detonated remotely. Other officials said the blast may have been from a roadside bomb.

A Somali lawmaker was assassinated and another wounded on Monday by a car bomb in Mogadishu, the prime minister said, the latest in a series of bomb attacks in the conflict-ravaged capital.

"Somalia has today lost a committed parliamentarian who worked tirelessly to serve the people of Somalia and help rebuild our country," Prime Minister Abdiweli Sheikh Ahmed said in a statement, referring to slain MP Isak Mohamed.