Police gather near a barricade during a protest in May in Bujumbura, Burundi. (Goran Tomasevic/Reuters)

TO THE international commitment to prevent mass atrocities, Burundi now presents a critical test. Violent political turmoil has embroiled the East African country since President Pierre Nkurunziza’s decision in April to seek a third term in office, though the country’s constitution limits presidents to two. Mr. Nkurunziza staged presidential elections in July, despite protests and a boycott by opposition parties. Since April, 240 people have died and 200,000 Burundians have fled to neighboring countries.

Burundi’s current crisis has been largely political rather than ethnic. But government rhetoric in Burundi carries chilling similarities to the hate speech that helped trigger the 1994 genocide in neighboring Rwanda. Last week, Mr. Nkurunziza demanded that citizens in particular neighborhoods turn over weapons, lest they be “dealt with as enemies of the nation.” On Oct. 29, Burundi’s senate president, Reverien Ndikuriyo, said, “Today the police shoot in the legs . . . but when the day comes that we tell them to go to work, do not come crying to us.” The phrase “Go to work” was a code used in Rwanda by Hutu extremists to instruct people to slaughter ethnic Tutsis. Nearly 800,000 were killed. For citizens in Burundi, which has the same Hutu-Tutsi makeup as Rwanda and lost 300,000 people in its own 12-year ethnic war, these words are unambiguous and unacceptable. The United States and other governments must continue to condemn any threatening speech and make clear that there will be strong consequences for such rhetoric.

Now is the moment for decisive and coordinated international pressure to prevent a descent into chaos. Targeted attacks, arbitrary detentions, crackdowns on media and high-profile assassinations have been on the rise in Burundi since August. The army is showing signs of fracture. On Thursday, the U.N. Security Council unanimously adopted a resolution condemning the violence and weighing options to increase the U.N. presence in the country. The African Union is urging that the government of Burundi and the opposition meet for urgent talks either in Addis Ababa, Ethi­o­pia, or Kampala, Uganda. But regional mediation efforts, led by Ugandan President Yoweri Museveni, have not yet borne fruit.

Last month , the African Union indicated its willingness to impose sanctions, travel bans and asset freezes on those in Burundi who perpetuate violence. It has also indicated a desire to launch investigations into human rights violations there. Importantly, the A.U.’s Peace and Security Council has requested the expediting of contingency planning to deploy troops to Burundi should the situation continue to escalate. The United States and other concerned nations should back both the A.U. and the U.N. efforts with the necessary aid and logistical assistance in order for the threat of sanctions and peacekeeper deployments to be made credible.

For too long, Mr. Nkurunziza’s government has been dragging Burundi closer to the brink. The world should spare no effort to prevent another East African mass atrocity.