Spanish coast guards rescued more than 170 migrants crossing the Mediterranean to Europe from northern Africa in four separate boats, they said Saturday.
Morocco notified Spain's coast guards that a boat had been spotted trying to cross the Alboran Sea, the westernmost portion of the Mediterranean that ends with the Strait of Gibraltar before connecting with the Atlantic Ocean.
As rescuers set off, they were told that three other boats carrying migrants had also been seen in the same area.
One of them was spotted by a plane helping EU border agency Frontex with surveillance, the other by a ferry, and the third by people on a Spanish naval base on Alboran Island, which lies between Morocco and Spain.
In all, 173 migrants from sub-Saharan Africa were rescued and taken by ship to the Spanish ports of Almeria and Motril, a coast guard spokesman said.
According to the International Organization for Migration, 2,426 migrants arrived in Spain by sea between January 1 and the end of April.
This still represents a small percentage of the more than 45,000 who crossed the Mediterranean to Italy, Greece, Spain and Cyprus over the period.