Secretary-General Ban Ki-moon warned Thursday that violence in the east African country of Burundi could worsen and spill across its borders.

The U.N. chief commended the U.N. Security Council's decision to visit the country next week, calling for stepped-up efforts "to break the political impasse and avert a humanitarian catastrophe."

He said Burundi's government must take steps to build confidence including releasing "prisoners of conscience" and lifting restrictions on civil society.

President Pierre Nkurunziza's decision to seek re-election last year has left Burundi on the brink of civil war.

The capital, Bujumbura, has been hit by violence as opponents and supporters of Nkurunziza target each other in gun, rocket and grenade attacks. The violence has spread to the provinces and there has been a wave of extrajudicial killings that human rights activists blame on the security forces.

A confidential report from the U.N. peacekeeping department to the Security Council, obtained Wednesday by The Associated Press, said peacekeeping troops should be deployed to Burundi only as a last resort if violence worsens.

It warned that if U.N. peacekeepers are sent, they would be "ill-equipped" to deal with widespread human rights violations that could amount to genocide.

The report makes clear that the best option in the event of escalating violence would be intervention by a single country or a coalition of nations.

But it said the focus now should be on trying to promote political dialogue and the deployment of an African Union Prevention and Protection Mission, which Burundi has not accepted. Those two goals will be the focus of a planned visit by the 15-member Security Council to Burundi, after a stop in Addis Ababa, Ethiopia, from Jan. 21-24.

The report paints a grim picture of a deteriorating political and security situation including a trend of high-profile assassinations, the killing of at least 400 people since April 2015 and more than 230,000 people fleeing the country. Burundi is one of the world's poorest and hungriest countries, with 60 percent of children under 5 suffering from stunting, and the current crisis has led several donors to threaten or withhold aid, according to the report.

The report said the best the United Nations could do quickly in the event of a civil war or widespread human rights violations "potentially amounting to genocide" would be to send about 4,000 troops from the U.N. peacekeeping mission in Congo to Burundi along with international police. That could be done in 12 hours if there were a 28-day preparation period, it said.

The U.N. could then deploy 8,000 to 10,000 troops in four to six months, but this would leave a serious gap "during which a high level of violence against civilians can be expected," the report said.