BEIJING –

⁠Japan has expressed its regret over the break-in at the Chinese embassy in Tokyo by a knife-wielding Japanese military officer, but that is “far from enough,” the ​Chinese foreign ministry said on ‌Friday.

The Japanese ‌side has not discussed the ​details of the incident, Lin Jian, spokesperson at the foreign ministry, told a regular news conference. Minoru ⁠Kihara, Japan’s most senior government spokesperson, described the incident ⁠on Tuesday as regrettable and said the government would take measures to ​prevent any recurrence.

The incident threatens to exacerbate Sino-Japanese ties. Relations ⁠have already deteriorated ​since November when the Japanese prime ​minister said Japan could deploy its ​military ‌if a Chinese move against Taiwan also threatened its territory.

“The Japanese side has expressed deep regret to the Chinese side regarding ‌this incident, but this is far from sufficient,” said Lin. “We once again urge the Japanese side to conduct a thorough investigation as soon as ​possible ​and provide China with a responsible ​explanation.”

Japan’s Defense Minister Shinjiro Koizumi said on ⁠Friday that the incident was “truly regrettable” and that his ministry was “fully cooperating” with the police investigation underway.

“We will also respond strictly ​once the facts have been established,” he said.