BISHKEK (Reuters) - Kyrgyz President Almazbek Atambayev raised the stakes in his standoff with political rival Omurbek Tekebayev on Monday, ordering prosecutors to look into corruption allegations against Tekebayev, which the parliament deputy denies.

Kyrgyzstan's President Almazbek Atambayev addresses a news conference in Berlin, April 1, 2015. REUTERS/Fabrizio Bensch/File Photo

The deepening rift between two political heavyweights could destabilize the volatile Central Asian nation which has seen two leaders overthrown by violent protests since 2005.

Tekebayev, who had previously backed pro-Russian Atambayev and was a member of his parliamentary coalition until last month, has become one of the main critics of the president after Atambayev proposed to boost the powers of the executive.

On Monday, Atambayev’s office said the state security service had obtained documents from the government of Belize showing Tekebayev, along with two other people, was set to benefit from a sale of assets by an offshore company.

Atambayev’s office said the offshore company was believed to be owned by the family of ex-president Kurmanbek Bakiyev, who was deposed and fled the country in 2010. The sale mentioned in the documents never took place because the government nationalized the assets in question.

Tekebayev denied any wrongdoing and said the move was politically motivated. The two other people mentioned in the Belize papers are members of his Ata Meken party and served as prosecutor general and justice minister respectively in April 2012, the date on the document published by the president’s office.

“This is 100 percent fake,” he told Reuters. “This is a primitive provocation they have come up with... because we oppose the referendum (on executive powers)”.

The mostly Muslim nation of 6 million will vote in a national referendum on Dec. 11 on a package of changes to the constitution which boost the powers of prime minister and the executive in general.

Atambayev’s opponents have said the reform could allow him to become a powerful prime minister once he steps down as president next year. Atambayev, 60, who is not allowed to run for a second term, has denied having such plans.

Both Atambayev and Tekebayev were among the leaders of the 2005 and 2010 protests and open confrontation between the two could lead to another wave of instability in the former Soviet republic which hosts a Russian military airbase.