The April 22-24 talks coincided with a decision by South Korea and Japan to toughen political and economic pressure on Pyongyang in order to speed up the process of denuclearization on the Korean peninsula.
"The talks were constructive and led to significant progress," the Korean Central News Agency cited an anonymous source in North Korean Foreign Ministry as saying, without revealing further details.
The United States, which is involved in the six-party denuclearization talks along with China, Russia, Japan, and South Korea, suspects Pyongyang of pursuing a secret uranium enrichment program and selling nuclear technology to Syria.
The talks aimed at persuading North Korea to drop its nuclear ambitions in exchange for economic aid and diplomatic incentives stalled in January after the Communist regime missed the December 31 deadline to give a full account of its nuclear programs.