Senegal braced for a potential showdown on Monday as President Macky Sall prepared to make a long-awaited announcement on whether he plans to seek a controversial third term.

On the eve of Sall's nationwide address, his fiercest critic, Ousmane Sonko, urged the public to "come out en masse" and oppose him.

The president is due to make the announcement on national television at 8:00 pm (2000 GMT).

Deadly clashes erupted last month between Sonko supporters and the security forces, claiming at least 16 lives.

The turbulence has stained Senegal's image as a beacon of stability in West Africa, a region notorious for coups and civil war.

Sall, 61, was first elected in 2012 for a seven-year term and again in 2019 for a five-year term, following a constitutional revision of the presidential tenure.

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

Sall once campaigned against a third term by his predecessor, Abdoulaye Wade, who was in power from 2000 to 2012.

He also repeatedly said he would not seek a third mandate.

But he has no designated political successor and in recent months has been coy about another term, a position that has stoked tensions.

- Unrest -

Sonko, a fiery orator popular with Senegal's disaffected youth, paints Sall as corrupt and a would-be dictator.

"It's incumbent on all the Senegalese people to stand up, to face him," Sonko said on Sunday night.

"If we have to put up a fight, it must be definitive... the days and weeks to come will be crucial," he said in a video posted on social media.

Sonko was sentenced on June 1 to two years' jail for "corrupting" a young beauty salon worker, sparking protests which led to 16 deaths according to the government, 24 according to Amnesty International, and 30 according to Sonko's party.

The conviction makes him ineligible to stand in 2024.

Sonko says the case was crafted to prevent him from running, a charge authorities deny. He has been blocked in by the authorities at his home since May 28.

- 'Praying for peace' -

Residents of the Senegalese capital Dakar returned to work on Monday after a long weekend break for the Muslim festival of Tabaski.

Abdou Diagne, a 38-year-old car washer, said: "I don't want him (Sall) to stand again. We've already given him 12 years -- it's time for him to go and let somebody else take over.

"If he says otherwise, it's not a given that people will stand by with their arms folded," Diagne said.

"Either way, we are praying for peace."

Samba Fall, 50, said he believed Sall "will keep his word."

"I expect him to say 'I thank the people for the trust they have invested in me over these last 12 years, I have made my contribution towards building a harmonious Senegal and I won't be standing again, in line with the constitution'."

But, he predicted, if Sall announces a bid for a third term, "that will shake the country up."