Dozens of exhausted migrants arrived in a wooden boat on a beach in Spain's Canary Islands early on Friday amid a sharp rise in perilous crossings from Africa, with emergency personnel and a few stunned beachgoers rushing to help.

The boat carrying 64 people made it to the Las Burras beach on the island of Gran Canaria by its own means, authorities said. Eleven migrants were taken to hospitals, some by helicopter as four were in critical condition.

The number of migrants arriving irregularly by sea to the Canary Islands in the Atlantic Ocean soared by 160% between January and July 15 from a year ago, totalling almost 20,000 people, according to Spain's interior ministry.

Overall arrivals by sea to Spain, including across the mainland, grew by 88% to around 25,300 people.

Emergency personnel handed the migrants yellow foil blankets, while some were placed on stretchers. A police officer held a baby in his arms as he stood next to a woman being attended by medics.

Beachgoers, including children, looked on, while one tourist handed her water bottle to a migrant.

The route from Africa to the Canary Islands is the fastest-growing migration route in Europe, with irregular crossings up 303% from January to May from a year ago, according to the latest data from European border control agency Frontex.

Another boat, carrying 145 migrants, was rescued on Friday near Gran Canaria, authorities said.