Viktor Serdyuk told TASS that Ustin the tiger was roaming along the Amur River some six or seven kilometers away from the border on the Bolshoi Ussuriysky Island that is divided between China and Russia.
"The tiger can any moment turn back as he has already done on Saturday," the official said. He said that Chinese environmentalists were ready to monitor Ustin's movements as they are currently monitoring another stray tiger, Kuzya.
Kuzya is one of the three Siberian tigers tagged with tracking devices that Russian President Vladimir Putin helped release in the Far-Eastern Amur Region earlier this year. The animal was spotted in the Taipinggou nature reserve in north-eastern China in early October.
Kuzya is staying in China but does not walk away far from the Amur river that forms the border between Russia and China, the official said.
Kuzya and Ustin are two of the five tiger cubs found in the Far-Eastern taiga some two years ago. The cubs were taken to a special rehabilitation center and later released into the wild.
The Siberian tiger, also known as Amur tiger, is on the Red List of Threatened Species. In 2010, Russia launched a national strategy to protect the Siberian tiger, the largest of the five tiger species. According to World Wildlife Fund, some 450 Siberian tigers are left on the planet.