Angry crowds have demanded the death penalty for a Sudanese newspaper editor over an article allegedly questioning the parentage of the Prophet Muhammad.
The editor is reported to be a prominent Islamist
Hundreds of people waving banners and chanting "God is great" protested outside a court as Mohamed Taha Mohamed Ahmed was charged over the article.
His Al Wifaq newspaper is being suspended for three days from Friday.
The crowds were closely monitored by riot police, who clashed with the protesters on Thursday.
"Oh judges of the Sudan, defend the honour of the Prophet," read one banner.
"The court must execute him - this is an insult not to any ordinary man - this is an insult to a prophet," one man said.
The protesters made speeches through loudspeakers and handed out statements, demanding that the authorities hand Mr Taha over so they could kill him.
Mr Taha is a prominent Islamist journalist and has close ties to the Muslim Brotherhood political group.
He has not yet commented on the allegations against him but a journalist from his newspaper said it was a "big misunderstanding".
Those who renounce Islam face the death penalty in Sudan.
Ali Shumi, the head of Sudan's Press Council, said the article insulted the Prophet Muhammad.
He denied the charges were an assault on press freedom.
"Freedom of the press stops when it comes to respect for religions. Not just for Islam - if you said the same things about Jesus there would be the same punishment," he said.
The BBC's Jonah Fisher in Khartoum says that with more than 15 daily papers, Sudan professes to have press freedom but in practice a lot of self-censorship takes place and on occasion the heavy hand of the censor cuts out articles before they go to press.
A truck-load of soldiers has been stationed outside the Al Wifaq offices down a narrow dusty side street in central Khartoum.
Al Wifaq journalist Hamed Abdul-Latif says that the newspaper did not write the article but reprinted a piece written by renowned Islamic historian Maqreezi.
Mr Taha wrote a commentary next to the piece, rejecting the historian's version of events, Mr Hamed says.
Khartoum has been governed by strict Islamic Sharia law since 1983 - but our correspondent says that in recent years courts have shown a degree of flexibility in their interpretations of Islamic law.
The introduction of Sharia exacerbated a rebellion that had begun in the south earlier that year. The war officially ended with a peace agreement in December.