N'DJAMENA (Reuters) -Chadian opposition leader and current transitional prime minister Succes Masra on Thursday claimed he won the Central African nation's May 6 presidential election in the first round.

Masra, 40, a main opposition challenger in to transition president Mahamat Idriss Deby, made the announcement in a live broadcast on Facebook, ahead of a scheduled announcement of the provisional results by the country's electoral agency.

"We have won as a people thanks to you the people who put us in the lead in the first round according 90% of centralized results from ballot boxes, which confirm the victory in the first round," Masra said.

"I have thousands of proofs of this. You have it too since you yourself have documented the truth of the ballot box because you will know the truth and the truth will set you free," he added.

With tensions running high, large numbers of security forces deployed at major intersections in the capital N'Djamena ahead of the results announcement.

(Reporting by Bate Felix and Alessandra PrenticeEditing by Anait Miridzhanian and David Gregorio)