The merchant fuel ship which sank off the coast of Gabes in Tunisia on April 15, 2022, is seen in this handout picture taken in Rostov-on-Don, Russia November 12, 2017. [Reuters]

Tunisian authorities intensified efforts on Saturday to avoid an environmental disaster after a merchant fuel ship carrying one thousand tons of fuel sank off the coast of Gabes on Friday, two security sources told Reuters.

The Tunisian navy had rescued all seven crew members from the ship, which was heading from Equatorial Guinea to Malta, and sent a distress call seven miles away from the southern city of Gabes, the sources added.

The cause of the incident was bad weather, the environment ministry said, adding that water had seeped into the ship, reaching a height of two metres.

Authorities were working to avoid an environmental disaster and reduce any impact, the ministry said in a statement.

It said barriers would be set up to limit the spread of fuel and cordon off the ship, before suctioning the spillage.

The coast of Gabes has suffered major pollution for years, with environmental organisations saying industrial plants in the area have been dumping waste directly into the sea.

Some countries have offered to help Tunisia prevent damage to the environment after the sinking of the ship, the Tunisian defence ministry said on Sunday.

The ship heading from Equatorial Guinea to Malta sank on Friday and the Tunisian navy rescued all seven crew members. 

The vessel carried between 750 tonnes and one thousand tonnes of fuel and sent a distress call seven miles away from Gabes to which the Tunisian navy responded, officials, said.

The defence ministry said in a statement sent to Reuters that to control the environmental damage the Tunisian navy will work with countries that have expressed their desire to help.

Local media said that Italy had offered to help and that it is expected to send a naval vessel specialising in dealing with marine disasters.

On Saturday, Tunisian authorities opened an investigation into the ship's sinking, which the environment ministry said was caused by bad weather.

It said barriers would be set up to limit the spread of the fuel and cordon off the ship, before suctioning the spillage.

The coast of the southern city of Gabes has suffered major pollution for years, with environmental organisations saying industrial plants in the area have been dumping waste directly into the sea.