A French freelance reporter who wrote that eastern Sudan is "a volcano waiting to erupt" says he was ordered expelled by the Khartoum government but that his departure was blocked because he had no exit visa.
Mathieu Galtier, 29, said his colleague Maryline Dumas, 25, also a freelance correspondent, must also leave Sudan.
"The official reason is because our visa is finishing," Galtier told AFP.
But the pair believe they are no longer welcome because of their coverage last week of a university protest, as well as Galtier's article from Kassala state about tensions in the country's east.
The two had been due to fly out of Khartoum to Paris on Thursday night.
But Galtier told AFP they were not allowed to board the flight because they had no exit visa in their passports.
He said a security official told them the matter would be dealt with on Saturday, and that they could leave the following day.
Their expulsion coincides with what the US-based Human Rights Watch calls a "recent wave of repression" against Sudanese students, activists and opposition figures.
Galtier said he and Dumas were detained by security agents last week when they interviewed and photographed student protesters at Khartoum University.
He also published a controversial article in early December for IRIN, a news service of the United Nations humanitarian agency.
It quoted "a well-placed international official in Kassala" who compared the country's eastern Eritrea border region with a volcano. Within months, it could erupt into a conflict such as those already occurring in Sudan's South Kordofan and Blue Nile states, the official was quoted as saying.
Galtier, whose three-month journalist permit expired on Wednesday, said he and Dumas first arrived in Sudan about the middle of last year.
"The term of their residency finished and the government refused to renew it for them," said foreign ministry spokesman Al-Obeid Meruh.
In February 2009, a Canadian journalist, Heba Aly, was expelled from Sudan. She also worked for IRIN, as well as for the Christian Science Monitor and Bloomberg.
Pulitzer prize-winning American journalist Paul Salopek was detained in the Darfur region and held for a month on espionage charges in 2006.
Sudanese journalists are more frequent targets of the authorities, whose intelligence service has a reputation for visiting newspapers at night to demand that articles be removed, or barring their distribution altogether.
On Monday, officials shut down Rai al-Shaab, the newspaper of the opposition Popular Congress Party -- just months after it started publishing again following an earlier raid.
The country witnessed a sharp crackdown on press freedom after South Sudan's secession from Khartoum in July following decades of civil war and an overwhelming vote to separate.
Among its moves, Khartoum cancelled the licences of six newspapers because of their part ownership by southerners, who are no longer Sudanese nationals as required by Sudan's press law.© ANP/AFP