The number of illegal immigrants arriving in Spain's Canary Islands from the north-west coast of Africa over the past three days has hit 1,000.
Medical treatment is needed for many of the arrivals
Three more boatloads arrived on Sunday, swamping reception centres.
Spain's prime minister is sending his interior minister to Senegal on Monday for talks to try to stem the flow.
Jose Luis Rodriguez Zapatero also said Spain would next year double its aid for tackling African emigration from this year's 613m euros ($786m; £417m).
The regional government of the Canary Islands has urged the authorities in Madrid to act urgently over what it calls an immigration avalanche.
Some 17,000 illegal migrants have arrived in the Canaries from the African mainland this year. This number is more than three times higher than for the whole of 2005.
Hundreds of other migrants have died trying to make the crossing.
The latest immigrants, who travelled in several small boats, have been given medical treatment for the effects of hypothermia and dehydration.
The journey from Mauritania had been the favoured route to the European Union for migrants from Africa.
But stricter controls there and in Morocco have meant more are coming from Senegal.
The Red Cross says it believes 100,000 people may be waiting in Senegal for a chance to cross.
Spanish Interior Minister Alfredo Perez Rubalcaba is to visit Senegal on Monday to offer aid.
Mr Zapatero had interrupted his holiday in the Canaries to visit two overcrowded reception centres.
In announcing the doubling of the budget on tackling the issue, Mr Zapatero also called on the EU to take a stronger interest in the matter, AFP news agency said.
"The fight against poverty is the only way to overcome [illegal] immigration," he said.
In a separate incident near Sicily, up to 20 people were missing after an inflatable dinghy carrying north African migrants capsized.
The crew of an Italian fishing boat rescued 10 people clinging to wreckage 100km (62 miles) off the island of Lampedusa.
The incident came a day after another boat packed with 120 migrants sank in the same area, killing at least 10 and leaving another 40 missing.