Last year protesters clashed with police at Mr Taha's trial

Mohammed Taha ran the al-Wifaq paper and was taken from his home on Tuesday night by an unknown group of armed men.

Last year, he was put on trial for blasphemy after his pro-government paper reprinted an article questioning the parentage of the prophet Muhammad.

The charges were later dropped but if convicted of blasphemy under Sharia law, he could have been put to death.

The BBC's Jonah Fisher in Khartoum says no-one has claimed responsibility but suspicion will immediately turn to Sudan's hardline Islamic groups.

In May last year, thousands of people demonstrated outside a courtroom in central Khartoum calling for Mr Taha to be put to death.

After several emotionally charged days the case was adjourned and later quietly dropped.

Our correspondent says the killing of Mr Taha, an ally of Khartoum's Islamist government, will raise fears that extremist groups are once again active in Sudan.

Sudan provided a home for al-Qaeda leader Osama bin Laden in the 1990s and the country is still on the United States' list of states sponsoring terrorism.

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.