South Korea condemned North Korea's third nuclear test as a violation of U.N. resolutions, an "unacceptable threat" to peace and stability in the region and a "head-on challenge" to the international community.

The government also warned that Pyongyang will be seriously held accountable for its defiance in an official statement issued after President Lee Myung-bak held an emergency meeting of the National Security Council.

Lee was also to meet with President-elect Park Geun-hye to discuss the security crisis.

The nuclear test "is an unacceptable threat to peace and security on the Korean Peninsula and the region and a head-on challenge to the international community," said Chun Yung-woo, senior presidential secretary, reading a government statement.

"North Korea won't be able to avoid grave responsibility."

South Korea will try to take every possible measure to get North Korea to surrender its nuclear programs, including actions through the U.N. Security Council, based on the principle that it won't tolerate North Korean nuclear tests, the official said.

Chun also said the government will try to deploy longer-range missiles capable of striking all of North Korea at an early date. (Yonhap News)