South Korean jets fired warning shots after a Russian military plane violated South Korea's airspace on Tuesday, Seoul officials said, in the first such incident between the countries.

Three Russian military planes — two Tu-95 bombers and one A-50 airborne early warning and control aircraft — initially entered South Korea's air defence identification zone off its east coast before the A-50 intruded in South Korean airspace, the South's Defence Ministry said.

South Korean fighter jets then scrambled to the area, including F-16s, and fired 10 flares and 80 rounds from machine guns as warning shots, a ministry official said, requesting anonymity due to department rules.

The Russian reconnaissance aircraft left the area three minutes later but it returned and violated the South Korean airspace again later Tuesday, the ministry official said. He said the South Korean fighter jets fired warning shots again. Each time, the Russian plane didn't return fire, the official said.

A Russian A-50 airborne early warning and control training aircraft briefly violated South Korea's airspace twice on Tuesday, Seoul officials said. (Alexander Zemlianichenko, File/Associated Press)

It was the first time a foreign military plane has violated South Korean airspace since the end of the 1950-53 Korean War, according to South Korean officials.

The former Soviet Union supported North Korea and provided the country with weapons during the Korean War, which killed millions. In 1983, a Soviet air force fighter jet fired an air-to-air missile at a South Korean passenger plane that strayed into Soviet territory, killing all 269 people on board. Relations between Seoul and Moscow gradually improved, and they established diplomatic ties in 1990, a year before the breakup of the Soviet Union.

South Korea's Chung Eui-yong, chief of the National Security Office, sent a strong objection to Nikolai Patrushev, secretary of the Security Council of Russia, and asked the council to assess the incident and take appropriate action, the president's office said in a statement.

"We take a very grave view of this situation and, if it is repeated, we will take even stronger action," Chung said, according to South Korea's presidential office.

Russia's Ministry of Defence denied that its strategic bombers had violated South Korean air space and accused South Korean jets of carrying out dangerous manoeuvres that threatened its aircraft, the RIA news agency reported.

The defence ministry said this was not the first time that South Korean pilots had interfered with a Russian military flight over neutral waters.

China's foreign ministry, meanwhile, said that South Korea's air space identification zone is not a territorial airspace and all countries enjoy freedom of movement there.

Embassy officials summoned

South Korea's Foreign Ministry and the Joint Chiefs of Staff summoned Russia's acting ambassador and its defence attaché respectively to file a formal complaint with them. Official protests were also registered with Beijing when China's ambassador and defence attaché were summoned.

The airspace the Russian plane violated, according to South Korean officials, was above a group of South Korean-held islets roughly halfway between South Korea and Japan that has been a source of territorial disputes between them. Russia isn't a party in those disputes.

Japan on Tuesday criticized South Korea for taking action against a Russian plane over what Japan says is its airspace, after Japan lodged a protest against both South Korea and Russia over the incident.

"Takeshima is Japan's territory," Foreign Minister Taro Kono told a news conference, referring to an island claimed by both South Korea and Japan. South Korea calls the island Dokdo.

The three Russian planes had entered the South Korean air defence identification zone with two Chinese military planes. But it wasn't immediately known whether the two countries deliberately did so, according to the South Korean official.

The South Korean jets fired around 360 rounds of ammunition during the incident, a South Korean Joint Chiefs of Staff official said. Russia's defence ministry denied this and said South Korean pilots had not communicated with the Russian bombers.

Before their joint flights with the Russian planes, the Chinese planes entered South Korea's air defence identification zone off its southwest coast earlier Tuesday, according to the South Korean official. Chinese planes have occasionally entered South Korea's air defence identification zone in recent years.