Somalia's Islamists are accused of links to al-Qaeda
Two French security advisers seized in Somalia this week have been split up and are now being held by two different hard-line groups, reports say.
The pair were snatched by gunmen from a Mogadishu hotel on Tuesday and were being held by the Hizbul-Islam group.
But officials say the al-Shabab group wanted them and after a row, Hizbul-Islam handed one of the men over.
Al-Shabab has recently carried out several beheadings, amputations and stonings in the areas it controls.
They are allied with Hizbul-Islam against the UN-backed interim government and together control much of southern Somalia.
Both groups are said to have links to al-Qaeda and have been reinforced by foreign fighters.
The BBC's Somali Service editor Yusuf Garaad Omar says al-Shabab is known for being the more radical of the two groups.
He says the hostage held by al-Shabab fighters is likely to face greater problems because they care little for their public image and have carried out killings on camera.
A group of gunmen dressed in military uniform seized the men on Tuesday morning and handed them over to Hizbul-Islam.
The move apparently sparked a row with al-Shabab, which managed to persuade the other group to hand over one of the hostages.
An unnamed al-Shabab militant told Reuters the two men had been shared "to avoid clashes between Islamists".
Somali Foreign Minister Mohamed Abdullahi Omar urged the rebel groups not to politicise the situation.
"So far, it remains a monetary issue, not a political one," he told AFP news agency.
Somali Prime Minister Omar Abdirashid Ali Sharmarke, meanwhile, warned Hizbul-Islam they would "bear responsibility for any harmful action taken against the hostages".
The French advisers were reportedly helping to train the forces of government, which has recently appealed for foreign help to tackle the Islamists.
The US last month confirmed that it has sent weapons to the government, which is also being protected by some 4,000 African Union troops in Mogadishu.
Somalia has not had a functioning national government since 1991.
Moderate Islamist Sheikh Sharif Sheikh Ahmed was sworn in as president in January after UN-brokered peace talks.
He promised to introduce Sharia law but the hardliners accuse him of being a western stooge.