China has denied that its ships used weapons-targeting radar on Japanese naval forces, calling Japan’s allegations “irresponsible” and heightening tensions between the two neighbors.

“Japan’s claim that the Chinese navy used fire-control radar to point at a Japanese vessel and helicopter is not in line with the facts,” the Chinese defense ministry said on Friday.

“Top officials in the Japanese government are making irresponsible remarks, talking up the ‘China threat,’ creating a tense atmosphere and willfully misleading international public concern.”

The defence ministry confirmed both encounters but claimed the Japanese naval crew could have mistaken the signal from China’s search radar used to closely monitor Japanese patrol vessels.

Chinese defense expert Colondel Dai Xu said the warning of a fire-control radar signal could have been triggered by mistake.

Japanese Prime Minister Shinzo Abe denounced what he described as a “provocative” move from Beijing that could “seriously” escalate the maritime dispute over a group of islands in the East China Sea, known as Senkaku in Japan and Diaoyu in China.

Fire-control radar is used to provide targeting information to missiles as well as some naval artillery, and is often seen as a sign of hostile intent.