TOKYO (AP) — Japanese controls on exports of key materials used to make semiconductors and displays have taken effect, as South Korean officials vowed to fight back.

The Japanese government ordered the more stringent approval process for shipments of photo resists and other key chemicals as relations with its neighbor and U.S. ally deteriorated due to issues related to forced labor during World War II.

The president’s office said South Korea’s National Security Council met Thursday in Seoul, with members vowing to pursue diplomatic countermeasures.

It said the move is viewed as an “explicit breach of international law, including World Trade Organization regulations.”

Japanese officials insist the decision to end preferential treatment for such exports to South Korea was required because of a lack of trust that poses a risk to national security.