Senegal's main opposition coalition is vying to gain clout in legislative polls on Sunday that will set the scene for a presidential election in 2024 that could see President Macky Sall run for a controversial third term.

Tensions have run high in the politically stable West African country since violent protests broke out last year, after Sall's main opponent Ousmane Sonko, who came third in the last 2019 presidential election, was arrested on rape charges. Sonko denies the allegations.

Frustrations with economic hardship brought by the coronavirus pandemic have been stoked by fuel and food price hikes linked to the war in Ukraine - raising ire against a president accused of stifling his rivals and failing on promises to improve livelihoods.

Some opponents fear Sall will breach a constitutional two-term limit and run again in 2024, and option he has neither confirmed nor denied.

Amid growing discontent, opposition parties hope the ruling Benno Bokk Yakaar coalition will see its parliamentary majority slip below the 125 out of 165 seats it currently occupies in the National Assembly.

"Citizens have openly expressed ... fatigue in the face of soaring prices ... the high cost of living, poverty and lack of jobs," said Moussa Diaw, political science lecturer at Gaston Berger University in the northern city of Saint-Louis.

Senegal - an ocean-facing nation of around 17.5-million people driven mainly by agriculture, fishing and tourism - also suffered a freeze trade with land-locked neighbour Mali. Sanctions were imposed on Mali in January for failing to organise its own elections after a coup.

Inflation is expected to reach 5.5 percent this year, according to the International Monetary Fund, which revised its growth forecast down to around 5 percent last month.

Sall, who swept to power in 2012 and was elected again in 2019, hinged his campaigns on big-ticket construction projects such as a high-speed train line and a conference centre, as well as oil and gas production.

But critics say most of his achievements have mainly benefited Senegal's elite, despite improvements in rural infrastructure and electricity access during his presidency.

Many also accuse Sall of trying to eliminate his competition. Two major rivals were jailed on corruption charges in 2015 and 2018. Sonko is widely considered the latest victim of this trend.

The main opposition coalition Yewwi Askan Wi's national list for the legislative poll was disqualified on technical grounds, fuelling violent street protests across Senegal last month.

"The opposition has made remarkable gains among public opinion and youths," said Diaw.

"If the president runs for a third term ... the country could tip into confrontation and crisis."

In a municipal election in January, the ruling party lost major cities to the opposition.