More than 30 people have been killed and dozens wounded in clashes between ethnic groups in southern Somalia, near the border with Kenya.
Fighting started on Monday night between two clans, over control of the town of Bula Hawo.
The fighting also affected the Kenyan town of Mandera across the border, where seven people were injured.
Kenyan radio on Tuesday reported that an unidentified number of suspects had been arrested in the area.
The BBC's Bashkash Jugsodaay in the Kenyan town of Garissa said hundreds of people had crossed the border and sought refuge there.
He added that no camps had been set up to accommodate them, and that people were heavily dependent on help from friends and relatives.
Commercial gateway
The fighting started after some 200 fighters from a breakaway group from the Somali National Front (SNF) tried to retake the town from a rival faction.
The SNF has been divided by a struggle over its leadership since 1996.
"Fifteen of the dead were attacking militia, 10 were the ones who were defending the town and six are ordinary civilians caught by straight bullets," an eyewitness, who asked not to be named, told AFP news agency.
Bula Hawo is the gateway to Kenya and Ethiopia - commercial routes from Mogadishu to both countries pass through this town.
Kenyan police have been deployed along the border with Somalia to prevent militiamen from crossing over, Mandera district police chief Charles Narangwi said.
He said the police had been warned a week earlier of plans to take over the town.
Since the toppling of the regime of Siad Barre in 1991, Somalia has been torn apart by warlords who have fragmented the country and fought among themselves for territorial control.