A suspected North Korean cyber-espionage group last year targeted an entity in Japan associated with the U.N. missions on sanctions and human rights violations involving Pyongyang, a U.S. cybersecurity firm said Tuesday.

California-based FireEye Inc. said the group it tracks as APT37 also spied on companies in Vietnam and the Middle East. FireEye did not identify any of the entities and corporations.

The North Korean group dubbed Reaper -- which FireEye believes has been active since at least 2012 -- "expanded its targeting beyond the Korean peninsula to include Japan, Vietnam and the Middle East" in 2017.

"We assess with high confidence that this activity is carried out on behalf of the North Korean government given malware development artifacts and targeting that aligns with North Korean state interests," FireEye said in a report.

Prior to that, APT37 primarily targeted the government and the private sector of South Korea. From 2014 to 2017, APT37 spying concentrated on the South Korean government, military, defense industry and media sector.

"We judge that APT37's primary mission is covert intelligence gathering in support of North Korea's strategic, military, political and economic interests," the report said.

Aside from Japan, APT37 last year targeted a Middle Eastern company that entered into a joint venture with the North Korean government to provide telecommunications service to the country.

Other targets included a Vietnamese trading company, as well as North Korean defectors and those involved in North Korean human rights issues, according to the report.

"APT37 has expanded its operations in both scope and sophistication," it said, citing the spread of its espionage into a wider range of industry verticals including chemicals, electronics, manufacturing, aerospace, automotive and healthcare entities.

"We anticipate APT37 will be leveraged more and more in previously unfamiliar roles and regions, especially as pressure mounts on their sponsor."