Published: Dec 17, 2010 7:34 PM EST
Updated: Dec 17, 2010 4:35 PM EST

UNITED NATIONS (AP) - Secretary-General Ban Ki-moon is urging North Korea to show restraint and calling on both Koreas to reduce tensions on the Korean peninsula.

The U.N. chief's comments Friday followed Pyongyang's warning that if Seoul goes ahead with planned artillery drills on a front-line island in the coming days it will respond with a bigger attack than it did on Nov. 23 when its shelling killed four South Koreans.

Ban, a former South Korean foreign minister, called the Nov. 23 attack on the tiny island of Yeonpyeong "one of the gravest provocations since the end of Korean war."

The secretary-general also called North Korea's recent disclosure of a new uranium enrichment facility "quite alarming."

(Copyright 2010 by The Associated Press. All Rights Reserved.)