Somaliland soldiers were attacked on Saturday by militia, state television reported, despite a ceasefire imposed after heavy fighting earlier this week in the breakaway state.

Somaliland, which has claimed independence from Somalia since 1991, has never been recognised internationally but is often seen as a beacon of stability in a chaotic region.

However, political unease has surged in recent months, and this week the UN said at least 20 people were killed after fighting erupted between government forces and militias in the contested town of Las Anod.

The town is claimed by both semi-autonomous Puntland -- a northern state in Somalia -- and Somaliland.

Abdiqani Mahamoud Ateye, Somaliland's defence minister, on Friday announced on Twitter an "unconditional ceasefire."

However, Somaliland National TV reported on Saturday that the army in Las Anod had been "attacked by terrorist militia."

"The National Army successfully defended themselves from the attack and are currently on high alert in their military base in Las Anod," the broadcaster wrote on Twitter.

The head of the militia held a press conference on Saturday, accusing the Somaliland army of instigating the latest violence.

"They announced a ceasefire last night but started the fire this morning and are shelling the town," said Garad Jama Garad Ali, adding that a doctor had been killed.

UN High Commissioner for Human Rights Volker Turk said Tuesday that the outbreak of violence came "just a month after at least 20,000 people were displaced by clashes" in the disputed town.

Control of Las Anod, located along a key trade corridor, has changed hands several times in recent decades.