SEOUL - South Korea says its jets fired hundreds of warning shots at a Russian surveillance plane that entered its airspace on Tuesday.
Officials said the plane twice violated the airspace over the Dokdo/Takeshima islands, which are occupied by Seoul but also claimed by Japan.
South Korea's Ministry of Defence said it scrambled fighter jets in response and fired 360 warning shots.
Russia has denied violating the country's airspace.
Moscow said two of its bombers carried out a planned drill over "neutral waters" and denied any warning shots were fired by South Korean jets.
This is the first incident of its kind between Russia and South Korea.
South Korea's military said the aircraft was one of three Russian and two Chinese military aircraft that entered the Korea Air Defense Identification Zone (KADIZ) on Tuesday morning.
Overseas aircraft must identify themselves before entering the KADIZ.
Russian and Chinese bombers and reconnaissance planes have occasionally entered the zone in recent years.
However, South Korea said one of the Russian planes - an A-50 reconnaissance aircraft - flew further and entered the country's territorial airspace at around 09:00 local time (00:00 GMT).
South Korean F-15 and F-16 planes were deployed to intercept it.
The head of South Korea's National Security Office, Chung Eui-yong, has lodged a strong objection with the Security Council of Russia, and asked the council to take appropriate action.
"We take a very grave view of this situation and, if it is repeated, we will take even stronger action," the South Korean president's office quoted Mr Chung as saying.
There has been no comment from China.(FA)