Crowds of people have marched in Sudan's capital Khartoum to call for a tougher sentence for a British teacher imprisoned for insulting religion.
Gillian Gibbons, 54, from Liverpool, was jailed for 15 days on Thursday after allowing children in her class to name a teddy bear Muhammad.
Some reports said protesters had called for her to be shot. Her lawyer said she was later moved for her own safety.
Muslim Labour peer Lord Ahmed is on his way to Sudan to push for her release.
Lord Ahmed, who is being accompanied by the Conservatives' Baroness Sayeeda Warsi, expects to meet President Omar al-Bashir and possibly the chief justice. He is travelling at the invitation of the Sudanese government.
The Foreign Office said Mrs Gibbons had been visited again by consular staff on Friday and that she was "well", but it could not confirm where she was being held.
A spokeswoman said: "We are pursuing diplomatic contacts with the Sudanese government, we are continuing to do so and will throughout the weekend both in London and Khartoum.
"We are continuing to search for a swift resolution of this issue."
The Foreign Office said it had been in touch with Lord Ahmed about his trip to Sudan but added that it was a private visit.
The BBC's Adam Mynott in Khartoum said Mrs Gibbons was initially held in a women's prison, but was later moved to a secret location following the protests.
The marchers took to the streets after Friday prayers to denounce the sentence as too lenient.
The protesters gathered in Martyrs Square, outside the presidential palace in the capital, many of them carrying knives and sticks.
Some news agencies reported thousands of people took part in the protest, but a BBC reporter at the scene said up to a thousand marchers turned out.
According to some agencies, some of the protesters chanted: "Shame, shame on the UK", "No tolerance - execution" and "Kill her, kill her by firing squad".
One demonstrator told reporters that it was unacceptable to take a toy and call it Muhammad.
"We can't accept it from anybody. Even if they can do that in Europe, they cannot do it here in Sudan. We ask our rulers and judges to review what they have said. Fifteen days is not enough."
Hundreds of riot police were deployed but they did not break up the demonstration.
The Foreign Office said it was seeking more details about the protest.
Prime Minister Gordon Brown has been in touch with Mrs Gibbons' family for a second time, speaking to a close relative of the teacher.
Foreign Secretary David Miliband has expressed "in the strongest terms" the UK's concern at her detention.
He said there were no plans to issue advice to British nationals living and working in Sudan in the light of the trouble, but diplomatic staff were keeping "a close eye" on the situation.
The Archbishop of Canterbury, Rowan Williams, said he could not "see any justification" for the sentence, calling it an "absurdly disproportionate response" to a "minor cultural faux pas".
The Federation of Student Islamic Societies (Fosis), which represents more than 90,000 Muslim students in the UK and Ireland, said it was "deeply concerned" at what was a "gravely disproportionate" verdict.
The federation's president, Ali Alhadithi, said: "What we have here is a case of cultural misunderstandings, and the delicacies of the matter demonstrate that it was not the intention of Gillian Gibbons to imply any offence against Islam or Muslims.
"We hope that the Sudanese authorities will take immediate action to secure a safe release for Gillian Gibbons."
In September, Mrs Gibbons allowed her class of primary school pupils to name the teddy bear Muhammad as part of a study of animals and their habitats.
The court heard that she was arrested on Sunday after another member of staff at Unity High School complained to the Ministry of Education.
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