The Gulf state of Qatar says Russia arrested two of its citizens after Qatar charged two Russians over the death of a former rebel Chechen leader.
Russia had been seeking Yanderbiyev's extradition
A Qatari foreign ministry official was quoted as saying two Qatari wrestlers were detained as they passed through Moscow airport on their way to Serbia.
Russia has not commented on the report.
The ministry said it happened the same day Qatar announced it had charged two Russian spies over the car bomb death in Qatar of Zelimkhan Yanderbiyev.
Russia has denied the two intelligence agents were involved in Yanderbiyev's death and has demanded they be freed.
Qatar's state news agency QNA quoted the spokesman as saying the two wrestlers were arrested when they arrived at the airport on their way to Serbia to take part in a qualifying contest for the 2004 Olympic Games.
It said the men were detained on Thursday - the day Qatar announced it had charged the Russians over the blast which killed Yanderbiyev on 13 February.
QNA said Qatari authorities were in touch with Russia over the Qataris' arrests and that Moscow is expected to respond on Monday.
Russia accused Qatar of aiding terrorism by allowing Yanderbiyev to live in the country for the past three years.
Moscow blamed Yanderbiyev for the deaths of hundreds of Russians and had asked Qatar to extradite him on charges of terrorism and links to the al-Qaeda network.
Yanderbiyev was president from 1996 to 1997 of the breakaway republic of Chechnya, where insurgents have been fighting for independence from Moscow for nearly a decade.