Russia protested South Korea's issuing of a travel warning to the country, which came on the heels of the two recent attacks on South Koreans.

Russia's foreign ministry Friday said Seoul's decision to designate Russia as a travel warning zone was "not justified."

Some Russian media outlets reported bilateral relations are bound to be compromised since South Korea issued the travel warning, on top of its summoning of the Russian ambassador to Seoul to lodge a protest, Yonhap News Agency said Saturday.

This year marks the 20th anniversary for the two countries to establish diplomatic ties.

In response, South Korea sought Russia's understanding on its decision, saying the temporary measure was unavoidable against the backdrop of a series of attacks on South Korean students studying in Russia.

South Korea on Thursday said that all of Russia, except for the southern Kavkaz region, has been designated as a level 1 warning zone ``temporarily'' from March 11 to May 31.

A level 1 travel warning advises tourists and visitors to take precautions while traveling.

Kavkaz remains as a level 3 restricted zone due to the possibility of terrorist activities in Chechnya.

The South Korean government also said Korean residents in Russia should be cautions to ensure their safety, including not going outside alone or at night.

The latest incident occurred when a 29-year-old student was heading home after parting from his friends. Two masked Russians attacked the man, leaving him critically wounded.

The incident came just a month after a 22-year-old South Korean student was killed in the Siberian city of Barnaul, the capital of the Altai region, after being beaten and stabbed in what was believed to be a racially motivated hate crime.