Japanese Prime Minister Shinzo Abe said he and U.S. President Donald Trump agreed on Sunday that the international community must step up its response to North Korea after Pyongyang announced it had tested a hydrogen bomb.

Abe said he had agreed separately with Russian President Vladimir Putin to cooperate on North Korea.

"President Trump and I shared the view that we cannot overlook North Korea's reckless act and that the international community must show its resolve by applying stronger pressure than had so far been used", Abe told reporters after the call.

"We again confirmed that Japan and the United States are 100 percent together."

It was their second phone call of the day and their fourth since North Korea fired a missile over Japan on Tuesday.

Abe said he and Putin agreed that "North Korea's reckless act is a serious threat" and that they would maintain close contact on the issue.

He noted that he and the Russian leader are scheduled to meet this week on the sidelines of a gathering in Vladivostok.