Al Shabaab militants are leaving their stronghold in Somali city of Kismayo as Africa Mission in Somalia (Amisom) troops prepare to capture the port.
Residents in Kismayo told the BBC that the fighters from the Islamist militant group have been leaving on buses and trucks, taking heavy equipment with them.
Kismayo is the group’s main base in its fight against the Somali government, which has been converging on the town with African Union (AU) soldiers.
But Al Shabaab denies the reports, saying they have fought off AU forces.
Muhammad Usman Arus, a spokesman for the al-Qaeda-affiliated group, told the BBC that Al Shabaab had killed around Kenyan and Somali troops and pushed them back from Kismayo.
“We are in Kismayo – this is a propaganda war. The Kenyan and Somali forces have already broken off and gone back to their positions,” he said.
Local residents in the port city said it is calm, but some claimed Al Shabab had left behind armed youths with orders to shoot anyone believed to be against the group.
African Union troops who include Kenya Defence Forces have been slowly advancing towards Kismayo for months.
Analysts say that losing their strategic stronghold would be a major blow to Al Shabaab, although Mr Arus said the militants would fight on regardless.
In July, a UN report said the export of charcoal from Kismayo and Merca helped Al Shabaab generate millions of dollars – despite a UN Security Council ban on countries buying charcoal from Somalia.
The report accused the United Arab Emirates and Saudi Arabia of failing to uphold the ban.