Three people are missing and presumed drowned after a migrant boat was shipwrecked in the central Mediterranean, although almost 40 others on board were rescued, German aid group ResQship said on Saturday.

Tunisian fishermen were first on the scene on Friday evening when ResQship's vessel, the Nadir, arrived to help, a spokeswoman told AFP.

"When Nadir arrived, the fishermen had already taken aboard 38 people who were in the water. They told us that there are three people missing," she said.

The incident occurred southeast of the Italian island of Lampedusa, halfway on the route from the Tunisian city of Sfax.

The charity said survivors were taken by the Italian coastguard to Lampedusa, where the reception centre has for weeks been overwhelmed by the number of arrivals.

More than 42,000 people have arrived on Italy's shores since the start of 2023, almost four times the number in the same period last year, according to interior ministry figures.

Many of those attempting the crossing from north Africa to Europe to do not make it.

The period of January to March 2023 was the deadliest first quarter for migrants in the central Mediterranean since 2017, the United Nations said on April 12, with 441 lives lost.