HONG KONG — China and Vietnam appear to have reached at least a temporary impasse over a giant drilling rig sent by a state-controlled Chinese oil company to a site in the South China Sea between the Vietnamese coastline and a cluster of disputed islands, as the confrontation has continued to raise thorny issues of international law.

Col. Pham Quang Oanh, deputy chairman of the political department of Vietnam’s Coast Guard, said that as many as 15 Chinese ships had sprayed a Vietnamese vessel at the site with water cannons on Monday. He denied a report in Vietnamese news media that the vessel had used water cannons to fire back.

Over the weekend, Prime Minister Nguyen Tan Dung of Vietnam asked fellow leaders of the Association of Southeast Asian Nations at a summit meeting for support in confronting China. But the government of Myanmar, the host of the meeting, issued only an oblique statement on Monday expressing “serious concern” over the developments in the South China Sea, without mentioning China by name.

Hua Chunying, spokeswoman for the Chinese Foreign Ministry, said at a briefing on Monday that China and Vietnam had “14 communications” last week concerning the oil rig, and that they were continuing to communicate about it. She was not specific about what was said, or what the basis of the communications had been.