The personal information of British army, navy and air force members has been hacked in a significant data breach, raising alarm over a growing threat from cyberattacks by hostile states, Britain’s defense secretary said on Tuesday.

The attack targeted a third-party payroll system used by Britain’s Ministry of Defense, exposing the names and bank details of serving members of the armed forces and some veterans, as well as a small number of addresses.

The payroll system, which is not connected to the defense ministry’s own internal network, has been taken offline and the government did not publicly blame anyone for the data breach, or confirm claims by some lawmakers who pointed the finger at China.

“We do have indications that this was the suspected work of a malign actor and we cannot rule out state involvement,” Grant Shapps, the defense secretary, said in a statement to Parliament. “This incident is further proof that the UK is facing rising and evolving threats,” he said, adding, “The world is, I’m afraid, becoming somewhat more dangerous.”

Mr. Shapps said that an investigation had been launched into the data breach from the system run by SSCL, a contractor which also runs some business services for London’s Metropolitan Police. Only a “tiny number” of addresses had leaked, he added.

Earlier, Britain’s prime minister Rishi Sunak declined to speculate on the source of the attack but told broadcasters that the Ministry of Defense had taken the network offline, and was supporting those affected.