"No one lives who insults the Prophet," chanted the Sudanese protesters - some of them armed with knives and clubs -- after they left Friday prayer services in Khartoum.
Some protesters burned newspapers that contained pictures of Gillian Gibbons, 54, who was sentenced to 15 days in jail and deportation on Thursday just days after her arrest. She avoided the more serious punishment of 40 lashes.
Britain's foreign minister has said he was "extremely disappointed" with the verdict and called in the Sudanese ambassador for an immediate explanation.
The Sudanese Embassy in London called the situation a "storm in a teacup," the BBC reported.
A spokesman for the British embassy in Khartoum said that the British consul and deputy ambassador saw Gibbons on Friday and reported that she was well, according to a Reuters report.
A lawyer for Gibbons said she was relocated from a women's prison for her safety.
Several hundred protesters made a brief stop at the closed but heavily guarded Unity High School, where she worked, but they did not try to go inside. Five truckloads of police in riot gear guarded the school.
The protesters then marched to the British embassy where several hundred surrounded the ambassador's residence and chanted religious slogans. There were no reports of violence.
Gibbons was arrested Sunday after a school staff member complained that she allowed her 7-year-old students to name a teddy bear Muhammad. Giving the name of the prophet to an animal or a toy could be considered insulting to Muslims.
Archbishop of Canterbury Rowan Williams said Gibbons' prosecution and conviction was "an absurdly disproportionate response to what is at worst a cultural faux pas."
The case put Sudan's government in a tough position -- facing the anger of Britain on one side and potential trouble from powerful Islamic hard-liners on the other. Many saw the 15-day sentence as an attempt to appease both sides, the AP reported.
The incident has placed further strain on relations between Sudan, which has been plagued by war, famine and disease in recent years, and Western nations.
International experts estimate that 200,000 people have died and 2.5 million have been driven from their homes in ethnic and political conflict in western Sudan's Darfur region since a revolt by mostly non-Arab rebels in 2003.
On Friday, Sudanese congregated in the capital city's Martyrs Square outside the presidential palace, where hundreds of riot police were deployed. The anti-Gibbons rally lasted about an hour.