The revelation contradicts what the UPDF Spokesperson Brigadier Richard Karemire had said that four soldiers had died in a statement issued on Sunday evening.
The president explained that two vehicles of the enemy force entered one of the three sites attacked. "One vehicle was detonated and killed eight of our soldiers. May their souls rest in eternal peace. I extend condolences to their families."
The President, using his official Twitter handle @KagutaMuseveni, also said the UPDF had killed 36 al-shabaab militants contrary to the 22 stated by the UPDF spokesperson in Kampala and 30 as stated by the UPDF spokesperson in Somalia, Ceaser Olweny.
The Alshabab raided the African Union Mission to Somalia (AMISOM) base at Quoryole, Bulomareer and Golwein in Lower Shabelle region in Somalia.
Buulo Mareer is located some 130 kilometres southwest of the capital Mogadishu.
Eight vehicles including two vehicle born improvised explosives were destroyed by AMISOM forces.
President Museveni praised the army for foiling what he called "the bold but adventurous strategy of Al-Shabaab." He said the AMISOM force was alert, the reason they managed to repulse the enemy.
"With constant vigilance, victory is assured. I congratulate our soldiers for the good work they did yesterday, the death of eight of our soldiers notwithstanding," he said.
Called to comment on the statement by the President, Brigadier Richard Karemire said the additional deaths were from those who sustained injuries. He says by the time the army said four were dead they were four, but some who were injured have since died.
Karemire could not specify the day of the other deaths.
According to Karemire some soldiers had sustained injuries, but currently six UPDF soldiers remain injured, the same number he had given in the initial statement on Sunday evening, signed by his deputy, Lt Col Deo Akiiki.
Just like it happened with previous attacks, there has been conflicting figures on the number of dead and injured on both sides, with different media sources quoting different numbers.
The UK's Guardian online reports that at least 46 UPDF soldiers were killed in double car bomb suicide attacks, quoting local officials in Mogadishu. The report quotes Abdi Nur Hashi, a Somali military colonel who also said one Somali soldier had died and several others were injured.
The New York Times and Reuters give a much high number of causality figures, with both saying 59 Amisom soldiers were killed in the attack.
The special representative of the chairperson of the African Union Commission for Somalia, Francisco Madeira in a press statement issued on April 2 says at least 30 al-shabaab militants were killed, while four soldiers of Amisom were killed and six sustained injuries.
Karemire had insisted that the number of soldiers he gave out was the correct one.
The situation is similar to the one after the July 30, 2017 attack when UPDF said it had lost 12 soldiers while the militants said it had killed 39 Ugandan soldiers.
In September 2015, al-shabaab militants carried out an attack at the Amisom base in Janaale district in Somalia with reports indicating that 50 AMISOM soldiers had died, while the Somali military said 37 soldiers died.
The UPDF disputed this through the then spokesperson Paddy Ankunda who tweeted that the estimates of more than 50 deaths were a fabrication, insisting later that only 10 Ugandan soldiers had been killed in Somalia.
Days later, however, President Museveni who was on a visit to Japan told the media that 19 Ugandan soldiers had been killed in the Janaale attack, adding that six others were in action.
Uganda was the first country to deploy in Somalia in 2007 and contributes the biggest contingent of the 22,000-strong Amisom force.
The African Union plans to scale down its force and gradually hand over security operations to the Somali national army by 2020.
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