Left; Fernando Bengoechea / Beateworks / Corbis: Reuters British primary school teacher Gillian Gibbons has been arrested in Sudan, accused of insulting Islam's Prophet by letting her class of 7-year-olds name a teddy bear Mohammed.

It probably seemed like the most innocent of ideas to the newly arrived teacher from England, still settling into life in the Sudanese capital Khartoum. She asked her class of six- and seven-year-olds to dress up and name a teddy bear, and keep a diary of his outings. She hoped it would provide material for projects for the rest of the year. And it might have, except for the name the children chose for their bear: Muhammad.

Now Gillian Gibbons, 54, is spending her second night in a Sudanese prison, accused of insulting Islam's Prophet. She faces a public lashing or up to six months in prison if found guilty on charges of blasphemy. And Unity High School  one of a number of exclusive British-run schools in the Sudanese capital  has been closed as staff fear reprisals from Islamic extremists. Robert Boulos, the school's director, said the incident had been blown out of all proportion, but added that the school would remain closed until January to let ill feelings blow over.

"This was a completely innocent mistake," he said in an office decorated with sepia photographs dating back to the school's colonial heyday. "Miss Gibbons would have never wanted to insult Islam."

Police raided the school, where Gibbons also lives, on Sunday.

"We tried to reason with them but we felt they were coming under strong pressure from Islamic courts," said Boulos. "There were men with big beards asking where she was and saying they wanted to kill her."

A similar angry crowd had gathered by the time she arrived at the Khartoum police station where she is being held.

Unity, founded early in the last century, is one of several British schools run along Christian lines in an overwhelmingly Muslim country. Its high brick walls shut out the dust of everyday Sudanese life, transporting the visitor into the shady courtyard of an Oxbridge college or English private school. Many of its pupils come from well-to-do Sudanese families keen for their children to get the best education that money can buy. But Sudan is ruled by religious conservatives. Sharia law was introduced in 1991; alcohol is banned and women must wear headscarves. Convicted criminals are routinely flogged or executed.

The bizarre turn of events that led to the teacher's arrest began in September, soon after she arrived in the country, according to colleagues who have rallied in her support. Her young class was due to study the behavior and habitat of bears, so she suggested that pupils bring in a teddy bear to serve as a case study. A seven-year-old girl brought in her favorite cuddly toy and the rest of the class was invited to name him. After considering the names Hassan and Abdullah, they voted overwhelmingly in favor of Muhammad  the first name of the most popular boy in the class.

"No parents or teachers complained because they knew she had no bad intention," said Boulos. Until last week. Parents from another class raised concerns with the school. Then Sudan's feared police came calling at the weekend. Gibbons' colleagues said they feared a disgruntled member of staff may be using the issue to cause trouble.

Bishop Ezikiel Kondo, chairman of the school council, said: "The thing may be very simple, but they just may make it bigger. It's a kind of blackmail." Khartoum has exploded with anger at accusations of blasphemy in the past. Last year angry demonstrators denounced cartoons of the Prophet that appeared in Danish newspapers. And there have been protests at the actions of Zoe's Ark, a French charity accused of trying to smuggle children out of neighboring Chad.

Now everyone is waiting to see whether religious leaders or politicians will take their supporters onto the streets this time. Most parents arriving at the school gates were supportive of the British teacher. One mother, whose seven-year-old son was in Gibbons' class, said her family had not been offended by the name. "Our Prophet Muhammad tells us to be forgiving," she said. "So she should be released. She didn't mean any of this at all."