Somalia is investigating how a private Kenyan plane with coronavirus medical supplies crashed near the city of Baidoa, killing all six on board.

Police say the African Express aircraft crashed in flames just before it was due to land in Bardale on Monday.

Officials say the crash's cause is not clear but there has been speculation it might have been shot down.

Kenya's foreign affairs ministry says its investigators have been invited to join the Somali inquiry.

The crew was made up of two Kenyan and four Somali nationals.

The Islamist militant group al-Shabab has a presence in the area of Bardale, but the town and its airfield are held by Somali government soldiers and Ethiopian troops who are part of the African Union force in the country.

Ethiopia's defence spokesperson has denied its forces had any involvement in the incident in Bardale, which is about 300km (180 miles) north-west of the capital, Mogadishu.

Abdirashid Abdullahi Mohamed, a former Somali defence minister, is quoted by the Reuters news agency as saying that he had spoken to a witness at the airfield who said the plane appeared to have been shot down.

Kenya's foreign ministry has urged Kenyans and other humanitarian aircraft operating in the region to take precautions "in light of the unclear circumstances surrounding the incident".

"The aircraft was about to land at the Bardale airstrip when it crashed and burst into flames," Abdulahi Isack, a police official, is quoted as saying by the AFP news agency.

It had flown from Mogadishu to Baidoa and then continued to Bardale town before crashing.

The Kenyan Civil Aviation Authority says it lost contact with the plane at around 16:20 local time (13:20 GMT) - but did not know the exact time of the crash.

African Express Airways has told the BBC it has sent a team from Mogadishu to Bardale to help of the local authorities assess the situation and do an initial report on the crash.