Search and rescue operations are continuing off northwestern Senegal after a migrant boat capsized near the Lompoul dunes, killing at least 35 people and leaving an unknown number missing, emergency services said on Sunday.

Only one survivor has been found, while authorities have warned that the death toll could rise.

Senegal's Interior Ministry initially reported 21 deaths. The toll later rose to 34, according to the Senegalese Press Agency (APS) and migrant support group Action for Human Rights and Friendship, before emergency services confirmed at least 35 deaths on Sunday night.

The boat reportedly sank between Friday and Saturday near the Lompoul dunes in the Kebemer department, between Dakar and Saint-Louis. Saliou Diouf, founder of migrant aid group Boza Fii, said the bodies recovered on Saturday were Senegalese, although the nationalities of all those aboard remain unknown.

President Bassirou Diomaye Faye said state agencies and resources had been mobilized to search for the missing, assist survivors and support affected families. The interior minister is expected to visit the area.

The disaster highlights the dangers of the Atlantic migration route to Spain's Canary Islands. On Friday, Senegalese authorities intercepted another boat carrying 142 migrants last Friday from five West African countries.

Meanwhile, authorities on the Canary Island of El Hierro declared an emergency on Saturday after more than 3,300 migrants arrived in around 30 boats since the beginning of November.

Increased maritime patrols by Senegal, Mauritania and Morocco have pushed some migrant departures further south, extending the dangerous crossing from countries including Gambia, Guinea-Bissau and Guinea.