For devout Muslims, any physical depiction of Mohammed is considered blasphemous.

Prison and lashes

Gibbons faces up to six months in jail, 40 lashes and a fine if she is found guilty of "insulting or degrading any religion, its rites, beliefs and  sacred items or humiliating its believers", as stipulated in Sudan's penal code.

Some Islamic leaders in Sudan said on Wednesday that the law should be applied against Gibbons.

North Sudan's legal system is based on Sharia, which punishes blasphemy against Prophet Muhammad.

"What has happened was not haphazard or carried out of ignorance, but rather a calculated action and another ring in the circles of plotting against Islam," the Sudanese Assembly of the Ulemas said in a statement.

British response

The office of Gordon Brown, Britain's prime minister, said David Miliband, the country's foreign minister, wanted to see the Sudanese ambassador "as a matter of urgency".
  
The purpose of the meeting was "so we can get a clear explanation for the rationale behind the charges and a sense of what the next steps might be", a spokesman for the prime minister's office said.

Gibbons told British consular officials who visited her in Khartoum on Wednesday that she was being treated well by the authorities.

"Our consulate went to visit her this morning. She said she was okay and treated well," an embassy spokesman said.

Treated humanely

Zamrawi said Gibbons was being treated humanely.

"She is in a room and she has all the necessary things. She has seen her lawyer and is brought food," he said.

"She has basic rights. For us, she is innocent until her guilt has been proved ... Her relatives can visit her."

He said the authorities were working to ensure that Gibbon would not be exposed to angry mobs should she be released.

Sudan's education ministry will conduct an inquiry into the school to determine whether it had sought to cover-up the incident, Zamrawi said.