The United States has said that it has received assurances a Sudanese Christian woman has not, as reported, been re-arrested one day after a court annulled her death sentence for apostasy. 

Mariam Yahya Ibrahim and her family were detained as they tried to board a plane in Khartoum.

Ms Ibrahim, 27, was sentenced to death last month for converting to Christianity from Islam, however she was released yesterday following what the Sudanese government said was unprecedented international pressure.

She was freed by an appeal court and then sent to a secret location for her protection after her family reported receiving threats.

Her release was welcomed by human rights groups and Western governments that had voiced outrage at the death sentence.

US State Department spokeswoman Marie Harf said Washington has been informed by Sudan that "the family was temporarily detained at the airport for several hours by the government for questioning about issues related to their travel and, I think, travel documents. 

"They have not been arrested," she added.

"The government has assured us of their safety. The embassy has and will remain highly involved in working with the family and the government.

"We are engaging directly with Sudanese officials to secure their safe and swift departure from Sudan."

Ms Ibrahim's lawyer said she was sent to a police station in Khartoum for questioning over providing forged information.

Mohaned Mostafa said he was with her at the police station and police wanted to question her, but he could not give any further details.

Ms Ibrahim was born to a Muslim father and an Ethiopian Orthodox Christian mother and was convicted under Islamic sharia law that has been in force in Sudan since 1983 and outlaws religious conversions on pain of death.

Ms Ibrahim’s father abandoned the family when she was five, and she was raised according to her mother's faith.

The Roman Catholic Archdiocese of Khartoum said she joined the Catholic Church shortly before she married.