Japan’s space agency has suffered a series of cyber attacks since last year, officials said.

However, sensitive information relating to rockets and satellites was not affected, officials at the Japan Aerospace Exploration Agency (Jaxa), and it is continuing to investigate and take preventative measures.

Japan’s chief cabinet secretary Yoshimasa Hayashi acknowledged that Jaxa has suffered “a number of” cyber attacks since late last year.

Jaxa has investigated the extent of illegal access while shutting down the affected networks and verifying that they did not contain classified information about operations of rockets and satellites and national security, he said.

Mr Hayashi vowed to strengthen Japan’s ability to counter cyber attacks.

Japan has been accelerating a military build-up in response to China’s growing military might and is hoping to be able to develop a counter-strike ability, but experts say Tokyo will continue to need to rely heavily on the United States for launching long-range cruise missiles at targets.

Officials on Friday said they were not aware of any information leak from the cyber attacks.

Defence minister Minoru Kihara told reporters that the attacks on Jaxa have not affected his ministry, but that he is keeping a close watch on the investigation by the agency, which is one of his ministry’s key contractors.

Education and science minister Masahito Moriyama also told a news conference Friday that he believed there was no actual damage from the cyberattacks.

Officials said JAXA is currently working with the government’s cybersecurity team to introduce counter-measures.