The government on Friday froze the assets of the operator of a North Korean ship seized for smuggling arms, the Foreign Ministry announced, just as Tokyo is engaged in talks with Pyongyang to return Japanese citizens kidnapped decades ago by North Korean agents.

The sanction against Ocean Maritime Management, which operated the vessel detained near the Panama Canal a year ago carrying Soviet-era arms, follows similar steps by the United States and U.N. blacklisting of the North Korean firm in July.

It is not immediately clear how many assets, if any, Ocean Maritime Management holds in Japan, the Finance Ministry said.

Pyongyang in May agreed to reinvestigate the fate of Japanese citizens it abducted in the 1970s and 1980s. In return, Tokyo last month eased sanctions on the North, lifting travel curbs and allowing port calls of its ships for humanitarian purposes.

The sanctions lifted are separate from those imposed by Japan and the United Nations members after North Korea’s first nuclear test in 2006 that prohibit U.N. member states from arms trade with Pyongyang and financial transactions that facilitate such trade.

Prime Minister Shinzo Abe’s government needs to tread a fine line by not appearing too close to North Korea and thus undermining calls for it to abandon its nuclear and missile projects while maintaining sufficient ties to avoid derailing the kidnapping reinvestigation.

“We have no choice but to do what’s right, treating them (the North’s reinvestigation and arms smuggling) as separate things,” a Foreign Ministry official said. “We have made it clear that sanctions will be tightened as long as they carry on with their nuclear and missile programs. . . . They are well aware of that.”

Pyongyang admitted in 2002 to kidnapping 13 Japanese citizens. Five abductees and their families later returned to Japan. North Korea said the remaining eight were dead and that the issue was closed, but Japan has pressed for more information about their fate and others that it believes were kidnapped.