"[Bermet Akayeva] was released at precisely midnight [local time, or 7 p.m. GMT]," Maxim Maximovich told RIA Novosti. "She was asked during questioning to provide information about her parents, husband, and relatives."
Maximov said no documents authorizing her detention had been presented.
The Kyrgyz Prosecutor General's Office said Akayeva would be questioned in connection with investigation into her husband, Adil Toigonbayev, and brother, Aidar Akayev. Bermet's mother, Mairam Akayeva, who headed a charity foundation allegedly used as a channel for illegal money transactions, also features in the case, prosecutors said.
Toigonbayev, a businessman from Kazakhstan, and Aidar Akayev are accused of embezzlement of public funds. The investigation was opened after Askar Akayev fled the country. Askar Akayev has repeatedly denied accusations against his family members, and denounced his daughter's arrest.
"The arrest of my daughter on the border between Kazakhstan and Kyrgyzstan shows that all members of my family are permanently being followed," Askar Akayev said. "This is a premeditated political act."
He said Bermet had been crossing the border into Kyrgyzstan from Kazakhstan to visit her relatives when security officers stopped her, saying she was driving a stolen car.
Other sources said she had been traveling to Kyrgyzstan for a presentation of her book about last year's "tulip revolution," which led to the ouster of her father, who was accused of corruption and authoritarianism. Bermet was due to give a news conference Tuesday.
Askar Akayev said his daughter's detention was aimed at him, as Bermet had been already cleared off all charges. He said the incident was "total lawlessness," and asked Russia to mediate.
A criminal case against Bermet was dropped when she was stripped of a parliamentary mandate. She made it into parliament in February-March 2005, but the election results were invalidated over massive violations.