(Adds UN'S comment)
BUJUMBURA, April 17 (Reuters) - Burundi ordered a security adviser at the United Nations mission in the country to leave on Thursday, escalating a row that started with a warning by the U.N. last week of a possible outbreak of political violence.
Government officials in the tiny central African state reacted angrily to the warning by the U.N. mission on Wednesday, saying it was baseless and had possibly been made to justify an extension of its mandate beyond its December expiry date.
The warning was linked to a political crisis over planned changes to the constitution that could allow President Pierre Nkurunziza to run for a third term. Critics say the changes could upset the country's delicate ethnic power balance.
"A senior security adviser for the UN mission in Burundi has 48 hours to leave the country," said Willy Nyamitwe, deputy spokesman for Burundi's president.
"He is the one who produced a wrong report on an alleged plan to distribute weapons to youth groups affiliated to the ruling party."
The Twitter feed of the presidency named the adviser as Paul Dobbie. The U.N. said it would engage with Burundi on the expulsion of its official.
"We regret the decision by the government of Burundi to declare a U.N. staff member persona non grata. We'll address this matter with the government of Burundi through usual diplomatic channels," said U.N. spokesman Stephane Dujarric.
Burundi's political stand-off has raised the risk of another explosion in a volatile region already grappling with unrest in eastern Democratic Republic of Congo, South Sudan and Central African Republic.
The country fought a 12-year civil war that ended in 2005. (Reporting by Patrick Nduwimana and Michelle Nichols in New York; Writing by Duncan Miriri; Editing by Andrew Roche)