A Russian official has said a military jet's intrusion into South Korean territorial airspace was not intentional, according to Seoul's presidential office.
The official expressed "deep regret" to the defence ministry and blamed a technical glitch, South Korea said.
However Russia has not officially commented. Earlier it furiously denied entering South Korean airspace.
Also Read:
Tuesday's incident caused alarm across the region.
Russia's defence ministry had earlier said its plane was taking part in a joint air patrol by Russian and Chinese warplanes over the Sea of Japan and the East China Sea - the first ever air patrol between the two countries.
China's defence ministry has also denied any of the planes had entered the territorial air space of any country.
But South Korea's Blue House said in a briefing on Wednesday that Russia had now said the violation was unintended and that it would immediately launch an investigation into the case.
"Moscow said if the aircraft flew according to an initially planned route, this incident would not have occurred," spokesman Yoon Do-han told reporters.
The alleged incursion happened over the disputed Dokdo/Takeshima islands, which are occupied by South Korea but also claimed by Japan.
