ATHENS (AFP) - Greek authorities said Friday they have banned a TV station from showing footage of a boat that was shipwrecked while being towed by the coastguard, killing up to 12 migrants.

The boat, capsized in late January, carrying 28 mostly Afghan men, women and children. Six bodies are thought still to be trapped in the wreckage.

The UN demanded an enquiry after it emerged that the boat was being towed by the Greek coastguard when it sank.

TV station Mega was planning to show footage of the shipwreck, which was found on Sunday. But the judge in charge of the enquiry said they were blocking use of the footage while his team concluded its investigation.

Ta Nea, Greece's leading newspaper, called the ban "preventative censorship" and an attack on the freedom of the press.

Journalist Stavros Theodorakis, who was preparing the TV programme, said: "If journalists had to ask the permission of the court to investigate cases, not one of my previous broadcasts would have been completed." Twelve people, mostly women and children, died in the shipwreck which was towed by Greek coastguards after being stopped off the island of Farmakonissi in southeastern Greece.

A judicial enquiry was launched after several survivors accused the coastguard of causing the boat to capsize by towing it too fast.

The Greek authorities have denied any mistreatment of migrants and denied accusations that the boat was being dragged towards the Turkish waters, in violation of international rules.

Many migrants drown each year in the Aegean Sea, the main gateway to the European Union people for people fleeing poverty and conflict in Asia and Africa.