Senegal's main opposition politician Ousmane Sonko on Thursday warned of "indescribable chaos" if he is unable to contest February's election, in his first comments since President Macky Sall confirmed he would not seek another term.

"There will be no elections in this country, or there will be indescribable chaos if President Macky Sall uses judicial tricks to prevent my candidacy," Ousmane Sonko said in a virtual interview with the French outlet France 24.

Sonko, a firebrand politician and Sall's fiercest opponent, was sentenced last month to two years in prison for morally corrupting a young woman, a conviction that renders him ineligible to run for office.

The ruling led to the most serious unrest Senegal has seen in years, leaving 16 people dead, according to authorities, or around 30 dead, according to the opposition.

Sall, who is coming to the end of his second mandate, on Monday announced in a nationwide address that he would not seek a controversial third term in next year's election.

The constitution stipulates that a president cannot serve more than two terms — but Sall's supporters had argued the counter had been reset to zero thanks to a 2016 revision.

In recent months, he had remained coy about a third term, stoking ambiguity exploited by the opposition.

On Thursday, Sonko said the president had made the decision not to run, "not because he is a democrat," but because of "popular and international pressure."

He said there is no reason to congratulate him for it.

Though he said those in power are determined to eliminate him from the presidential race, Sonko flagged that he was "ready to forgive" and even to "forget" if permitted to run.

Calling for free, transparent and inclusive elections, Sonko said he hoped Sall ended his term well "and that he and his family will be able to leave in peace."

He also said that currently, he is not in contact with Sall.

Security forces have blocked Sonko in his home in the capital Dakar since May 28, several days before the court ruling.