Italian authorities have detained seven crew members of a fishing boat after they were spotted allegedly helping migrants cross the Mediterranean.

A surveillance plane belonging to the European Union’s border force, Frontex, captured footage of the smugglers at work, about 100 kilometres south of the island of Lampedusa.

Frontex alleges the fishing boat transferred 81 migrants to a smaller vessel, which then headed towards Italy.

The fishing vessel headed back towards Libya. An Italian patrol boat gave chase and intercepted the vessel north of the Libyan coast.

The migrants, who had allegedly been left without water or any other supplies, were rescued and taken to Lampedusa.