GRAN CANARIA- About 80 African migrants packed aboard two fishing boats landed on the Spanish island of Gran Canaria on Tuesday, adding to the hundreds of new arrivals now stuck there while the coronavirus lockdown prevents transfers to the mainland.

The first boat docked at the port of Arguineguin with about 50 people aboard, 23 of whom are believed to be children.

"They arrived in good health, although a little dehydrated," said Gerardo Santana, head of the Red Cross on Gran Canaria.

A 16-year-old was taken to hospital with vomiting and nausea.

A second vessel carrying 30 men, a woman and four children, landed on the rocky coast of San Bartolome de Tirajana, where medics took temperatures and handed out blankets and masks.

Both groups will be tested for coronavirus and will undergo a two-week quarantine, a government spokeswoman said.

State news agency EFE reported that three recently-arrived migrants had tested positive for the virus and were being held in isolation.

Illegal migration to the islands, in the Atlantic Ocean west of Morocco, has risen nearly seven-fold so far this year to 2,113 people as of May 15, despite a 29% drop in overall seaborne arrivals to Spain, according to Interior Ministry data.

Heightened security across the Mediterranean is likely to be driving more migrants to risk the perilous Atlantic crossing, said Helena Malena, head of the Caminando Fronteras non-governmental organization, which monitors migratory flows.

"The migrants are still there...they have to get out somehow, so the mafias open up more dangerous routes."

Red Cross centres on the islands are overloaded and the humanitarian organization has resorted to putting up migrants in empty sports halls.

"We are saturated," Raul Baez Quintana, head of the Red Cross' Canary Islands humanitarian aid program, told Reuters. "As long as they keep coming we'll have to keep on taking them in, at least until the state of emergency is over."

(Reporting by Borja Suarez and Paola Luelmo in Gran Canaria and Nathan Allen in Madrid; Editing by Andrei Khalip and Angus MacSwan) ((Nathan.Allen@thomsonreuters.com;))