The 6.5km swim between Asia and Europe saw over 2,800 participants from 81 countries
Istanbul: A Russian athlete went missing during the annual Bosphorus cross-continental swimming race in Istanbul, the organising committee said on Monday.
The 6.5-kilometre (4-mile) swim between Asia and Europe took place on Sunday, with more than 2,800 participants from 81 countries.
With the Bosphorus Strait, one of the world's busiest shipping lanes, temporarily closed to traffic, the race began at the neighbourhood on the Asian side and ended in Kurucesme on the European side.
"We would like to inform the public about the efforts undertaken by our committee and official institutions following the discovery that Russian athlete Nikolai Svechnikov ... went missing during the race," the Turkish Olympic Committee said in a statement.
Russia's consulate general in Istanbul said it was in contact with Turkish authorities about the situation and confirmed Svechnikov's relatives had been informed
According to the official race website, swimmers have a time limit of two hours to complete the course, with the Turkish coast guard picking up anyone who does not finish within that time.
The Turkish Olympic Committee said the race began at 10:04 am (0704 GMT) with the last swimmer entering the water at 10:54 am.
The entire route was searched, and no swimmers remained in the area, it added.
An initial check found that three swimmers were missing, but this was later reduced to a single athlete, it said.
"This information was immediately shared with the coast guard command, the maritime police department, and the Istanbul governor's office, and search and rescue operations were ... immediately initiated," the committee said.
"We are working in full cooperation with the coast guard and police units to shed light on the incident."
Istanbul prosecutors have launched an investigation into the incident, the private DHA news agency reported.
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