Updated 3.50pm

At least eight people are dead and an unknown number missing after a migrant vessel and a Tunisian naval ship collided in Malta's search and rescue zone.

According to testimony from survivors, there were between 70 and 80 people on board, International Organization for Migration (IOM) spokesman Flavio Di Giacomo said. He said at least 20 people were missing.

The migrant vessel sank following the collision, Italian news agency ANSA reported.

In a statement, the Armed Forces of Malta confirmed that it was coordinating rescue efforts. 38 people were rescued by the Tunisian navy, the AFM said. Italian and Tunisian naval vessels were involved in rescue efforts, they added.

Initial reports had described the Tunisian vessel as a fishing boat, but a Tunisian government spokesman later told Nova News Agency that the vessel involved was a military ship. This was later confirmed by the AFM in its statement.

An AFM spokesman told Times of Malta a King Air aircraft had been sent to the area to better survey the situation. 

Italian media has reported that coast guard vessels from Lampedusa have been sent to the scene. According to Sky Italia, a high-speed patrol boat from the Italy's Guardia di Finanza and military ship have also been dispatched to aid with the rescue effort.

North African countries have stepped up efforts to block Mediterranean migrant crossings in recent months, with Libya's EU-funded coast guard adopting a particularly hostile stance towards migrant vessels and NGO rescue ships.

As Libya has cracked down on departing vessels, many people smugglers have shifted their operations further west to Tunisia and Morocco, with Spain seeing a record number of people landing on its shores this year so far.