Japan on Wednesday said that it was "regrettable" that a member of the Japanese military was arrested over the suspicion of breaking into the Chinese Embassy in Tokyo, as relations between the two Asian nations move from bad to worse.

The alleged incident took place on Tuesday morning, leading to a lodged protest by Beijing later in the day. China's Foreign Ministry had claimed the military personnel threatened to kill diplomats. 

"It is truly regrettable that a Self-Defense Forces member, who is expected to comply with the law, has been arrested on suspicion" of entering the embassy premises, said Minoru Kihara, the Japanese government's top spokesperson.

"Police are already conducting an investigation to clarify what happened and have implemented necessary measures to strengthen security" of the embassy, he told a press conference. "We will take necessary steps to prevent any recurrence of such incidents," he added.

On Wednesday, China's Foreign Ministry urged Japan to bring ⁠the ⁠full weight of the law against the suspect. It added that the Chinese Embassy was cooperating with Tokyo's police.

What do we know about the incident?

A police spokesperson told news agencies AP and AFP that the suspect was a 23-year-old and claimed to be a Japan Self-Defense Forces officer. He is said to have scaled a compound wall and was arrested around 9 a.m. local time (0000 GMT). 

The suspect told law enforcement that he was "hoping to meet the ambassador to tell him to refrain from making hardline remarks."

"If that request was rejected, I wanted to surprise him by killing myself," the suspect told police, according to Japanese media. The national broadcaster later reported that a knife was found at the scene. 

Japan's Ground Self-Defence Force (GSDF) confirmed that the suspect was a soldier.

After the incident, China's Foreign Ministry spokesperson Lin Jian said Beijing was "deeply shocked" and had lodged "a strong protest with the Japanese side."

He demanded Tokyo investigate the incident and punish the individual while taking preventative measures.

Meanwhile Japan responded saying it would take appropriate action and reinforce security for the embassy.

China and Japan's souring ties

Ties between China and Japan have deteriorated in recent months, after Japanese Prime Minister Sanae Takaichi made comments about the self-ruled island of Taiwan last November. The arch-conservative leader, only elected in October last year, suggested that Japan may use military intervention if China were to attack Taiwan.

China, which regards the democratic Island as part of its own territory, has not ruled out force to annex it and was furious over Takaichi's comments.

Edited by: Wesley Dockery