Russia has summoned the South Korean and US envoys to express "deep concern" about upcoming live-fire military exercises on an island shelled by North Korea last month.
The foreign ministry called for the drills to be cancelled to prevent tensions rising further in the region.
The Russian move followed a warning from North Korea of retaliation if the planned drills were held.
Yeonpyeong Island is very close to the disputed inter-Korean maritime border.
Four South Koreans - two civilians and two marines - were killed when North Korea shelled the island last month.
North Korea said the shelling was a response to military exercises there.
"We strongly call on South Korea to refrain from holding the planned artillery firing in order to prevent a further escalation of tensions on the Korean peninsula," the Russian foreign ministry said in a statement.
South Korea announced the exercises - the first since the 23 November incident - on Thursday.
It said the one-day drill would take place between 18-21 December and would be observed by about 20 representatives from the US-led UN Command.
Early on Friday, North Korea warned that the drills would lead to "self-defensive strikes".
"The intensity and scope of the strike will be more serious than the 23 November [shelling]", a report from state-run news agency KCNA said.
Responding to the North Korean warning, South Korea's defence ministry said in a statement that it did not need to "react to every single threat and unreasonable statement", suggesting that the drill would take place.
Since the 23 November incident, South Korea has strengthened its military presence on the island and pledged to use air power against any future attacks.
The warnings over the drills come amid a flurry of diplomatic activity to try to ease tensions on the Korean peninsula.
Senior American and Chinese foreign policy officials have been holding talks in Beijing.
And the governor of New Mexico, Bill Richardson - who in the past has acted as an unofficial US envoy to the North - is paying a visit to Pyongyang.