African Union leaders at a summit in Uganda have agreed to reinforce the AU peacekeeping force in Somalia to counter al-Shabab militants.

They approved a request to send 2,000 more troops to the Somali capital Mogadishu, officials said.

Rules of engagement will be changed to allow the troops to fire first if they are facing imminent attack.

Earlier, Ugandan President Yoweri Museveni had said the fight against al-Shabab must be stepped up.

Dozens of people were killed two weeks ago in two bomb attacks in Uganda's capital, Kampala, which al-Shabab said it carried out.

His call for a military offensive to defeat al-Shabab was not taken up by the African Union leaders. However, the force will now be able to carry out pre-emptive attacks against the hard-line Islamic insurgents.

The summit also approved requests for new equipment for the force. Troops from Uganda form a large part of the AU's Somalia peacekeeping mission.

Fragile government

The African leaders gathered in Kampala amid tight security and a heavy military presence.

Mr Museveni told AU delegates that "many of the organizers" of the attack had been arrested and their interrogation was "yielding very good information".

In a statement released before the meeting, Mr Museveni said the attacks would worsen al-Shabab's situation.

"These reactionary groups have now committed aggression against our country," the statement said. "We have a right of self-defense. We shall now go for them."

BBC East Africa correspondent Will Ross says there is concern that any offensive against al-Shabab could increase the number of civilian deaths and make the AU mission extremely unpopular with the Somali population.

About 5,000 AU troops from Uganda and Burundi are based in Mogadishu, propping up the fragile interim government.

Amisom (African Union Mission in Somalia) is engaged in frequent firefights with insurgents that control much of southern and central Somalia.

Sudan row

Meanwhile, Malawi President Bingu wa Mutharika renewed an attack on the UN for indicting Sudan's Omar al-Bashir on war crimes charges.

Mr Mutharika, the current head of the AU, said an International Criminal Court (ICC) arrest warrant for the Sudanese president on war crimes and genocide charges was "undermining African solidarity and African peace and security".

Mr Bashir is not attending the summit in Uganda, which is a signatory to the ICC.

His visit to Chad last week was his first to an ICC signatory since the warrant was issued in 2009. There was no attempt made to arrest him.

They observed a two-minute silence for the victims of the 11 July bomb attacks, which targeted people who were watching the football World Cup final at a Kampala restaurant and a sports ground