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

Three Russian military planes initially entered South Korea's air defence identification zone off its east coast before one of them entered the country's territorial sky, the South's Defence Ministry said.

South Korean fighter jets then scrambled to the area to fire warning shots, a ministry official said, requesting anonymity due to department rules.

The Russian plane left the area but it returned and violated the South Korean airspace again later on, the ministry official said.

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He said the South Korean fighter jets fired warning shots again. Each time, the Russian plane didn't return fire, the official said.

It was the first time a Russian military plane violated South Korean airspace, according to South Korean officials.

The airspace the Russian plane violated 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.

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.

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.

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South Korea's Defence Ministry said it plans to summon Russian and Chinese Embassy officials later Tuesday to register formal protests.

The ministry said South Korean warplanes "conducted a normal response" to the incursion, without giving further details.