• In the capital Dakar, security forces fired tear gas and stun grenades to disperse the crowds.
• A student died in clashes with police on Friday in the northern city of Saint-Louis.
Violent protests in Senegal against the postponement of presidential elections have spread across the country, with the first fatality reported.
A student died in clashes with police on Friday in the northern city of Saint-Louis, an opposition leader and a local hospital source said.
In the capital Dakar, security forces fired tear gas and stun grenades to disperse the crowds.
The 25 February elections were last week delayed by MPs until 15 December.
President Macky Sall had earlier called off the polls indefinitely, arguing this was needed to resolve a dispute over the eligibility of presidential candidates.
Lawmakers later extended Mr Sall's mandate by 10 months.
Opponents of the move have warned that Senegal's reputation as a bastion of democracy in an unstable region of West Africa is on the line.
Opposition leader Khalifa Sall, who is not related to the president, earlier called the election delay a "constitutional coup".
The death of the student in Saint-Louis was reported by Khalifa Sall in a post on social media.
"The hearts of all democrats bleed at this outburst of clashes provoked by the unjustified halting of the electoral process," he said.
The death was confirmed by a local hospital source speaking on condition of anonymity, and by an official at the university the student attended, according to the AFP news agency.
The Senegalese authorities have not publicly commented on the issue.
The country's mass protests erupted last weekend. On Friday, demonstrators in Dakar fought running battles with security forces, throwing stones and burning tyres.
President Sall has said he is not planning to run for office again - but his critics accuse him of either trying to cling on to power or unfairly influencing whoever succeeds him.
Twenty candidates had made the final list to contest the elections, but several more were excluded by the Constitutional Council, the judicial body that determines whether candidates have met the conditions required to run.
West Africa's regional bloc Ecowas on Tuesday pleaded for Senegal's political class to "take steps urgently to restore the electoral calendar" in line with the constitution.
Senegal has long been seen as one of the most stable democracies in West Africa. It is the only country in mainland West Africa that has never had a military coup.
It has had three largely peaceful handovers of power and never delayed a presidential election.