The migrants were tested for Covid-19 before being transferred onto a quarantine ship where they are expected to stay for two weeks as a precaution against the spread of coronavirus, a Reuters witness said.
Ocean Viking is still at sea.
Migrant boat departures from Libya and Tunisia to Italy and other parts of Europe have increased in recent months due to warmer weather.
According to the UN-affiliated International Organization for Migration, more than 1,100 people fleeing conflict and poverty in Africa and the Middle East have perished this year in the Mediterranean.