A report by a U.N. panel will accuse South Korea of failing to notify the Security Council of its shipments of petroleum products to North Korea in breach of international sanctions, diplomatic sources say.

It will be the first time for the sanctions committee on North Korea under the 15-member council to say that Seoul has violated U.N. sanctions against Pyongyang. South Korea has been stepping up efforts to improve relations with North Korea since last year.

The panel is also expected to say North Korea illegally sold fishing rights to other countries in contravention of Security Council resolutions.