The G7 gathered in Japan should not meddle with another country, China said on Thursday.
"The South China sea issue doesn't relate to the G7 and its members at all," said Foreign Ministry spokeswoman Hua Chunying at Thursday's daily briefing.
"We think the G7 should concentrate on dealing with its own internal issues rather than meddling with another country and that's something they should not concern themselves about.
"This would also benefit the G7 itself."
Hua's remarks backed up a state media editorial on Thursday that the G7 should "mind its own business rather than pointing fingers," Chinese state media said in an editorial Thursday.
Summit host Japan had a "hidden agenda," according to the piece in Beijing's state-owned Xinhua news agency, "to meddle in the South China Sea issue."
The group of seven leading industrialized "should mind its own business rather than pointing fingers at others and fuelling conflicts," the commentary said.
China claims a wide swathe of the sea, overlapping with territory claimed by Vietnam, the Philippines, Brunei, Malaysia and Taiwan.
G7 countries including the US have expressed concern over escalating tensions, which have seen Beijing reclaim land and build installations including airstrips on shoals in the disputed area.
G7 leaders are meeting for two days in the Japanese coastal city of Shima where they are expected to voice opposition to island construction and militarization of outposts in the South China Sea, without explicitly naming China.
Officially, the agenda will focus on the global economy and security.
US President Barack Obama this week announced the lifting of a decades-long US arms embargo on Vietnam, making it easier for Vietnam to import US weapons including maritime capabilities.
Obama was applauded by the Vietnamese audience in Hanoi Tuesday when he said "big nations should not bully smaller ones," in apparent reference to the South China Sea dispute.