Journalist Dawit Isaak is being held in harsh conditions at a high-security prison near the Eritrean capital, a Swedish newspaper reported Wednesday, quoting a former guard at the prison.

• “Release Swedish journalist Dawit Isaak”

Isaak is being held handcuffed nearly around the clock in solitary confinement in a windowless cell measuring only 12 square metres (130 square feet) at the secret prison, some 50 kilometres (30 miles) from Asmara, the Dagens Nyheter (DN) daily reported.

The information, the first in years to pinpoint Isaak's whereabouts or describe the conditions of his detention, came from a 37-year-old Eritrean refugee in Sweden who had worked at the Eiraeiro prison, the paper said, adding that for his security it would not reveal the man's identity.

An Eritrean with Swedish citizenship, Isaak was arrested in September 2001 along with a dozen newspaper owners, editors and journalists accused of being Ethiopian spies.

No charges have been filed and no trial has been held against the reporter, now 45.

Isaak, whose head had been shaved, was "thin" but considered by prison officials to be strong enough to require him to be shackled at all times during the day, according to the DN report.

A number of other high-profile prisoners, including former government ministers opposed to President Isaias Afeworki, were being held in the same prison, according to the paper's source.

Former foreign affairs minister Haide Woldetensae, former information minister Beraki Ghebreselasie and former fisheries minister Petros Solomon were all locked away at Eiraeiro, DN said.

Other reporters like Amanue Asrat and Fisahaye Yohannes were also being held there, as was film director Meriem Hagos, the paper said.

Around 15 of the initial 35 inmates at the seven-year-old high-security prison had died so far, while nine others were in very poor health, it reported.

Sweden's centre-right governement has been harshly criticised for not doing enough to secure Isaak's release, and DN pointed out that in the 3,118 days since the reporter was arrested, Stockholm's "silent diplomacy" approach had made little progress.

Foreign Minister Carl Bildt however insisted to the paper that much was being done behind closed doors.

"We do not send out a press release each time we make contact" with Asmara, he told DN, adding that "we will not switch to a (more outspoken) policy that we are convinced will bring about worse results."

Last month, the Council of Europe called on Eritrean authorities to release Isaak, who has held Swedish citizenship since 1992.