At least nine suspects had been detained in connection with Sierra's disappearance and death, Anatolian reported.
Yuri Zarutsky said he had been detained "for a crime" but refused to provide any details.
He had been detained while changing planes at John F Kennedy airport in New York.
Somali police official Mohamed Hassan told AFP news agency that more than 400 people had been detained.
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Officials declined to elaborate on how Mr. Tan was helping police or whether he had been detained.
The UKBA said steps would now be taken to deport all the people who had been detained.
The Paris talks began as NATO said 12 suspected guerrillas had been detained crossing into Kosovo from Albania.
He had been detained by the Russians for more than two weeks for allegedly working in Chechnya without accreditation.
At least 100 people were injured and a similar number had been detained by police across the country, they said.
The U.N. has received reports that international staff members of five non-governmental organizations had been detained for up to four hours.
King Abdullah also pardoned several Libyans who had been detained over an alleged plot to assassinate Abdullah when he was crown prince.
Ms Gaye, 38, said the raid was the third time Arouna had been detained - the first being when he was aged two.
One of the activists who made it through said 27 other people who had flown with her from Lyon, France, had been detained.
But the head of the police's Terrorist Investigation Division, Chandra Wakista, told the BBC that as many as 20 to 25 had been detained.
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Thursday, Iraqi officials announced announced that 11 senior officials in charge of security around the Foreign and Finance Ministries had been detained for questioning.
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Mark Topping, prosecuting, said since his arrest the boy had been detained under the Mental Health Act in secure accommodation in the West Midlands area.
The Congress-led government said the protesters had been detained because they had not accepted the police's restrictions on the number of fasting days and participants.
Mr Chidambaram added some 1, 300 people had been detained at different places in Delhi, with most of them being taken to a stadium in the city.
Russian news agencies reported that Lipatov had been detained in Stupino, a sprawling Moscow suburb where the Bolshoi owns summer houses used by its dancers and management.
He said he had been detained by the Pakistani intelligence services, and had been grilled by the CIA and FBI about his alleged links with the Taliban.
Mr Kirby said he had been detained because he was a risk to the public but no professional had realised that "he had presented this risk to himself".
Meantime, immigration officials said Tuesday they had released hundreds of immigrants who had been detained and were awaiting deportation proceedings to cut costs in advance of the sequester.
Mr. Tan "is currently assisting Singapore authorities in their investigations, " the police said, declining to elaborate on how he was helping police or whether he had been detained.
India's Home Secretary RK Singh said Mr Hazare had been detained because he said he "intended to defy prohibitory orders" and go on fast at a park in Delhi.
"We reject this type of bad police practice, " Commissioner Jose Humberto Ramirez said, saying that the police officials allegedly involved had been detained and would be investigated by prosecutors.
On Tuesday, activists reported that an Emirati who had been on religious pilgrimage in Saudi Arabia had been detained on Monday night and turned over to the UAE authorities.
City of London Police said they were "pleased" to hear he had been detained and were establishing contact with authorities in the Caribbean country, which has no extradition treaty with Britain.
The men had been detained in a room with no ventilation, even though the average temperature in the city at this time of the year is higher than 38C, it added.
Hours after the offensive began Thursday morning in Maysan, Iraq's Defense Ministry said 17 people had been detained, a weapons cache seized in Amara and weapons found near main roads and waterways.
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