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Edmund Kagire, Associated Press
In this photo taken Tuesday, April 21, 2015, Burundian refugee Jean de Dieu Niyibizi, 27, one of many who have crossed to Rwanda, speaks about his journey and why he fled, at the Gashora refugee camp, in the Bugesera district of Rwanda. More than 10,000 people from the East African nation of Burundi have crossed into neighboring Rwanda amid threats of violence ahead of elections, with many arriving saying they have been intimidated by thugs who support President Pierre Nkurunziza who may seek a third term.

BUJUMBURA, Burundi — Burundi's ruling party on Saturday nominated President Pierre Nkurunziza to be its candidate for a third term in elections on June 26, a move expected to stoke political tensions.

The party announced Saturday that Nkurunziza had been nominated unanimously and unopposed during a retreat for party leaders. On the streets of Bujumbura, Burundi's capital, armed police were immediately deployed after the announcement.

Burundi's constitution stipulates that a president can only serve for two terms, but Nkurunziza's party says he is eligible for another term as popularly elected president because for his first term he was elected by lawmakers. Critics say this is not a proper interpretation of the law and he should not serve a third term.

More than 10,000 Burundians have fled to neighboring Rwanda citing fears of election violence. Many of those in Rwanda say they left because of growing pressure to support Nkurunziza's party, which is known by its initials as CNDD-FDD. Others alleged violent activities by the ruling party's youth wing, known as Imbonerakure, according to the U.N. refugee agency.

Recently opposition groups have mounted pressure on Nkurunziza to retire, with some staging street protests against a third term. Police have used force to break up the rallies.

Earlier on Saturday before the ruling party announced its decision, opposition leader Agathon Rwasa urged Nkurunziza not to stand for another term, warning that any attempt to stay in power would destabilize the country. Rwasa told an independent radio broadcaster that Burundi is likely to descend into violence if the ruling party and the opposition do not start negotiations.

Nkurunziza came to power in 2005 after a peace process that ended civil war in Burundi, which has a history of ethnic strife.

Last week U.N. Human Rights Commissioner Zeid Ra'ad Al Hussein said Burundi was "at a crossroads," warning that failure to hold free elections could return Burundi to what he called a "deeply troubled, tragic and horrendously violent past."

Associated Press writers Rodney Muhumuza in Kampala, Uganda, and Edmund Kagire in Kigali, Rwanda, contributed to this report.