Meriam Ibrahim, the Christian woman released from death row in Sudan on Monday, was arrested with her husband and two children at Khartoum airport yesterday as the family attempted to leave the country.
Agents from the National Intelligence and Security Services detained the family just 24 hours after Ibrahim was released on the orders of the appeal court.
Her lawyer, Elshareef Mohammed, said more than 40 NISS officers held the family as they attempted to board a plane to the US. Ibrahim's husband, Daniel Wani, is an American citizen.
"It's very disappointing," Elshareef said. "They were very angry. They took us [the lawyers] outside, and took the family to a NISS detention centre."
He said the appeal court had quashed Ibrahim's conviction and there were no restrictions on her travelling. He added that political differences within the government over the case may have played a part in the arrests.
"I'm very concerned. When people do not respect the court, they might do anything,"said Elshareef.
Ibrahim, 27, had been sentenced to death for apostasy. She insisted that she had been brought up as a Christian, despite her father being Muslim. She was also sentenced to be publicly flogged for adultery following a court's ruling that her marriage to a Christian man was invalid.
After her release, Wani said he hoped the family would be able to start a new life in the US. Ibrahim, Wani and their two children were taken to a safe house following her release on Monday.
Ibrahim's case attracted international criticism, which intensified after she gave birth to a daughter while shackled to the floor of her prison cell. Her toddler son was kept in Omdurman women's prison with her.
More than one million people backed a campaign by Amnesty International to free her. Amnesty said it was investigating reports of the family's detention.
Ibrahim was convicted after the court insisted she was a Muslim because her father was a Muslim. She argued she had been brought up as a Christian after her father abandoned the family when she was six.
Following her conviction last month, she was given three days to renounce her faith or face a death sentence.
Then eight months pregnant, she was told that her death sentence would be deferred for two years to allow her to nurse her unborn baby.