A cargo plane transporting Ugandan soldiers to Somalia's capital caught fire as it landed at Mogadishu's airport, officials say.
Some 1,200 Ugandans have already arrived in Somalia this week
A Somali Islamic group has claimed it shot at the aircraft, but Uganda's army spokesman told the BBC investigations so far suggest a technical problem.
Paddy Ankunda said none of the seven soldiers on board were injured.
Some 1,700 Ugandan troops are being deployed to the country as part of an African Union peace mission to Somalia.
The AU force is taking over from Ethiopian troops who intervened to help the interim government oust the Union of Islamic Courts (UIC), which had held power for six months and restored some order to the anarchic country.
Mr Ankunda said initial investigations indicated that the plane, which was carrying seven soldiers and military equipment, caught fire following mechanical problems.
The BBC's Mohammed Olad in Mogadishu said all seven peacekeepers from Ugandan army and crew were unharmed and could be seen running out of the Algerian airforce plane that was covered by smoke coming from the centre and the rear.
Soon after, fire extinguishers and units of the Ugandan army, were sent to put the fire out, witnesses told our correspondent.
But in a notice posted on a Somali website linked to the ousted Islamists, the militant group The Popular Resistance Movement in the Land of Two Migrations claimed to have fired rockets at the plane.
"Two missiles hit at the center of the plane," said the statement signed by the co-ordinator of the group Hadith Aba Sadiq.
However, Somali's Deputy Defense Minister Salad Ali Jelle has denied the claims.
Late on Wednesday, gunmen attacked a Ugandan convoy with a rocket-propelled grenade. At least 10 civilians were killed in the blast and subsequent gun battle; two peacekeepers were wounded.
The AU plans an 8,000-strong force that will replace Ethiopian troops backing the government.
So far, the AU has managed to raise only about half of the 8,000 troops required. Burundi, Nigeria and Ghana are also expected to contribute.
Meanwhile, reports from Kismayo say some 2,000 Ethiopian soldiers withdrew from the port city on Thursday and were seen heading to Baidoa, the temporary seat of the interim government.
The Ethiopians used Kismayo as a point to launch attacks against the ousted Islamic fighters who fled to Ras Kamboni area.
Ethiopian Prime Minister Meles Zenawi had said his troops will leave Somalia soon after the AU troops were deployed.