A Venezuelan court has sentenced the country's key opposition leader Leopoldo Lopez to 13 years and nine months in prison for his role in last year's anti-government protest.

A judge found him guilty of inciting violence during violent protests in 2014, which led to the death of 43 people, reported BBC.

"Today it is reaffirmed once again that we live under a repressive, anti-democratic regime," Lopez's wife Lilian Tintori said on Friday, according to Reuters.

The 44-year-old Lopez, however, vowed to continue to protest and said the sentence was intended to bring down the spirits of anti-government protesters.

"Great causes merit great sacrifices. This sentence is not only against me, but it attempts to bring down the spirits of everyone who is fighting to have a better country," Lopez wrote on his Twitter account, according to CNN.

Opposition leaders in Venezuela denounced the sentence as a tyrannical move by President Nicolas Maduro's social administration.

The United States Secretary of State John Kerry said he was deeply "troubled" by Lopez's sentencing and called for his immediate release.

"The decision by the court raises great concern about the political nature of the judicial process and verdict, and the use of the Venezuelan judicial system to suppress and punish government critics," Kerry said in a press statement.