(Reuters) - President Isaias Afwerki has turned Eritrea into Africa's "biggest prison for the media" since 2001 and four journalists have died in captivity, Paris-based Reporters Without Borders (RSF) said on Monday. Eritrea, which RSF ranks as the worst abuser of media freedom in the world, permits no independent media and the state-run newspapers and television network do not allow stories that challenge the nation's leadership or its policies.

The government has described a free press as "incompatible" with Eritrean culture and last year President Isaias said no Eritrean should want or need to attack their own country.

"Around 30 journalists are currently held in its 314 prison camps and detention centres. Four of them have died as a result of the extremely cruel conditions in these prisons. Others have just disappeared," RSF said in a statement.

"Ruled with an iron hand by a small ultra-nationalist clique centered on Afeworki, this Red Sea country has been transformed in just a few years into a vast open prison, Africa's biggest prison for the media," it said.

Eritrea denies the existence of large prison camps in parts of the country off-limits to independent observers and says international rights groups invent statistics and anecdotes so they can follow their own business interests in Africa.

RSF said basic freedoms of the press were officially suspended in 2001 after some former members of Eritrea's ruling party began pressing for more democracy.

"Any hint of opposition is seen as a threat to national security. The privately-owned media no longer exist. There are just state media whose content is worthy of the Soviet era."

RSF says Eritrea is the worst abuser of press freedom in the world, ranking it below North Korea three years in a row.

One of the journalists arrested in 2001, Swedish-Eritrean citizen Dawit Isaak, has been promised a trial by Eritrean authorities, local Swedish media reported last month.

Rights groups and some opposition parties in Europe have called for a suspension of aid to the African nation.

Eritrea is on the cusp of a gold mining boom with some 16 companies now operating in the Red Sea state.

(Editing by George Obulutsa)