The Moroccan royal navy has rescued 615 illegal migrants off the Mediterranean sea, Morocco's army said in a statement on Monday.

According to the statement, during the weekend, units of the royal navy, operating in the Mediterranean, assisted some 31 inflatable boats, which were carrying the migrants, that ran into trouble while heading to Spain.

All individuals were safely returned to Moroccan ports and several of the boats carrying them sank because of their dilapidated condition, the same source said.

In recent months, Morocco has been witnessing a significant hike in illegal migration attempts.

Morocco thwarted at least 54,000 attempts to smuggle illegal migrants into Europe in the first eight months of 2018, compared with 39,000 attempts a year earlier, the Moroccan government said.