VIENTIANE, Laos — A summit of Southeast Asian countries issued a mild rebuke of China on Wednesday over its expansionist activities in the disputed South China Sea, and indirectly urged it to show restraint and not raise tensions.

In a victory for Beijing’s diplomatic, economic, and military clout, the Association of Southeast Asian Nations couldn’t even get all of its 10 members to agree that China was responsible for building islands in the disputed and resource-rich sea.

A statement issued at the end of the ASEAN summit said in regard to the South China Sea, ‘‘We remain seriously concerned over recent and ongoing developments,’’ without elaborating. It did not mention China by name.

China has recently developed shoals and coral reefs into seven islands with massive land reclamation work. Some of the islands have airstrips capable of handling military aircraft.

The statement underscores the problem ASEAN has had in dealing with China — not all of its members are willing to scold it.

Associated Press