Guinea's opposition candidate Cellou Dalein Diallo declared himself the winner of the West African country's presidential election Monday before the official results have been announced, setting up a tense showdown with the incumbent leader of a decade.

The party of President Alpha Conde, who is seeking a controversial third term, swiftly condemned Diallo's declaration as “irresponsible and dangerous.”

In its statement the ruling party called on "the competent institutions to take all necessary measures to prevent disorder and to prevent any attempt to destabilize the country and its legitimate institutions.

Guinea’s national election commission, meanwhile, reiterated that only it could release official results and would do so by the end of the week.

Monday's development marked a dramatic escalation in an already tense electoral season. 

Conde's decision to seek another term by having the constitution modified already had led to protests that left more than 50 people dead this year.

Diallo said his declaration was based on information gathered at polling stations by his party, the Union of Democratic Forces of Guinea. He did not give any figures to back up his claim.