Gunmen shot dead a Somali lawmaker in Mogadishu on Wednesday, a day after al Qaeda-linked rebels killed at least two people in a series of grenade attacks and said they would step up assaults in the capital.

It was not immediately clear who carried out the assassination of parliamentarian Aden Bule. Local residents blamed clan militia fighters.

Tuesday evening's strikes highlighted the ease at which al Shabaab militants are able to infiltrate the heart of the coastal city, which is meant to be under the control of government soldiers and an African Union force (AMISOM).

A grenade was hurled at the busy Howlwadag road last night, killing two people and injuring nine others, including soldiers, said ambulance coordinator Ali Musa, referring to the attack on a street through the city's main Bakara Market.

Al Shabaab claimed to have killed 15 government soldiers in four separate attacks. Twelve were killed as they patrolled the Howlwadag road, the rebels said. Other targets included the house of a former justice minister and a prominent local elder.

The militants, who are bracing for battle with Kenyan forces in southern Somalia, said Tuesday's grenades were just an introduction.

We are planning more serious attacks inside the capital, Mogadishu, Sheikh Abdiasis Abu Musab, an al Shabaab spokesman, told Reuters on Wednesday.

The militants pulled most of their fighters out of Mogadishu, epicentre of their almost five-year insurgency, in August amid reports of internal divisions and funding shortages.

GUNNED DOWN

Since then, the AMISOM peacekeeping force and government troops have been flushing out remnant insurgent fighters.

The United Nations estimates 98 percent of the capital is under the government's control -- the most since the overthrow of a dictator in 1991 threw the Horn of Africa country into conflict and left much of Mogadishu in the hands of warlords.

Security has improved since the militants retreated: men in flowing robes chat lazily on sidewalks over sweet tea, residents are returning to former rebel strongholds to rebuild homes and the daily crackle of gunfire and thud of mortars has subsided.

The murder of Bule, however, underscored the threat clan militia still pose, and the difficulties policing Mogadishu.

Two men armed with Ak 47 -rifles shot the lawmaker dead in front of his house. His body has not yet been carried from the spot, said resident Ali Aden, who witnessed the shooting.

I believe it was the clan militia who occupied his own house by force for years, he said, adding that Bule had ordered the security forces to evict the squatting fighters.

In a shift from more conventional street warfare, al Shabaab has increasingly resorted to suicide attacks and guerilla-style tactics. They claimed responsibility for an October 4 suicide truck bomb which killed more than 70 people.

AMISOM said the insurgents had melted into the population and troop numbers were insufficient to secure the entire city.

We know the fighters are still hiding among the population, Paddy Ankunda, AMISOM spokesman, told Reuters. It is the work of the government to do house-to-house inspections to capture the al Shabaab remnants.

Fighting to impose a harsh version of sharia law on the nation, al Shabaab is also readying to wage battle with troops from Kenya, which sent its forces across the border to crush the militants more than three weeks ago.

City dwellers feared recent security gains could come undone.

It seems (the government) will never control the grenades and other explosions, said Hassan Abdulle, who recently returned to live in the city.

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