Somalia's government has ordered the UN top envoy to the troubled country to leave, accusing him of "deliberately interfering with the country's sovereignty."
The order comes days after the official, Nicholas Haysom, raised concerns at the action of Somalia's UN-backed security services in recent violence that left several people dead.
"The Special Representative of the UN Secretary-General for Somalia, Nicholas Haysom, is no longer welcome in Somalia and cannot operate in the country," the foreign ministry said in a statement late Tuesday.
There was no immediate reaction from the UN mission in Somalia.
Somalia's security forces used force to put down three days of demonstrations in the south-western town of Baidoa on 13-15 December, with at least 15 people killed and 300 people arrested, according to the UN.
Protesters were angry at the arrest of Muktar Robow, a former Islamist leader who was vying for post of regional presidency.
Robow, who defected from the jihadist Al-Shabaab movement in 2017, was detained by the government accused of seeking to "undermine stability", and flown to the capital Mogadishu.
Robow's run for office exposed the tensions between Somalia's federal states, which want greater autonomy from a national administration keen to safeguard its central powers.
The UN mission in Somalia is tasked with supporting peace efforts and the strengthening of government institutions in the Horn of Africa nation, which was left ruined by decades of civil war.
As part of that, the UN supports police officers, including with stipend salary payments, logistics, uniforms and training.
Haysom wrote to the Somali government on December 30, requesting details of the legal basis of the arrest of Robow, as well as calling for investigations into the deaths in the protests following his detention.
The UN mission in Somalia faces frequent attacks.
On Tuesday, three people were wounded including two UN staff members when gunmen fired a barrage of mortars into the main UN base in Mogadishu.
The Shabaab, an Al-Qaeda affiliate fighting to overthrow the internationally backed government, claimed responsibility for the attack.
Haysom, a South African lawyer and experienced diplomat who was previously the UN special envoy to Sudan and South Sudan, was appointed to the post in Somalia September 2018.