Somalia's national army has taken control of part of the biggest city in South West state, two weeks after regional officials said they were severing ties with the federal government in the capital Mogadishu, local residents said.

The city of Baidoa, the administrative capital of South West state, is home to international peacekeepers and humanitarian agencies in an area affected by drought, conflict and displacement.

Residents said fighting erupted between the national army and troops loyal to the South West state administration on Monday and that the army was now in control in parts of the city about 245 km (150 miles) northwest of Mogadishu.

"Federal forces have taken over Baidoa, ... it is now calm ... but it looks like a ghost town," local elder Adan Hussein told Reuters.

A shopkeeper in Baidoa, Hussein Abdullahi, said there were federal troops in his part of the city and they were in control there.

Captain Osman Nur, a national army officer, said most of Baidoa was under federal control.

Abdullahi Haji Hassan, South West state's interior minister, did not respond to phone calls and messages seeking comment.

Many residents have fled Baidoa over the past week and some aid agencies suspended their activities, fearing clashes could erupt between the army and regional forces.

The dispute between South West state is the latest sign of strain in the Horn of Africa country's fragile federal system.

The South West administration says relations with Mogadishu worsened after the federal government pushed through constitutional amendments opposed by some state leaders.

Somalia's defence ministry said in a post on X that the army was carrying out operations against militant group al Shabaab on the outskirts of Baidoa on Monday when it came under attack from armed militias reportedly taking orders from the leader of South West state.

It said the army repelled the attack, captured some militia members and remained in control of most areas from which the attack was launched.