SEOUL, June 30 (RIA Novosti) - North Korea seems to be pressing ahead with uranium enrichment, with a view to making more nuclear weapons, Yonhap agency said on Tuesday, citing South Korea's defense minister.

"It seems it is definitely being pursued," Defense Minister Lee Sang-hee told a parliamentary hearing, adding that a uranium enrichment program was easier to hide than reprocessing of plutonium.

"Uranium enrichment can be conducted in a space as small as 600 square meters," the minister said. "It is easier to hide than plutonium reprocessing."

The North's two underground nuclear tests, in May this year and in October 2006, used plutonium-based nuclear bombs.

North Korea vowed earlier this month to go ahead with uranium enrichment following a UN Security Council resolution that expands sanctions on the Communist state for the latest May 25 nuclear test.

South Korea says the North has about 40 kg of plutonium, enough to produce at least six warheads.

Six-nation talks to persuade Pyongyang to drop its nuclear program stalled after the North quit the process in April, accusing the U.S. of failure to meet its obligations under an aid-for-disarmament deal.

North Korea's recent military activities, which also included a series of missile launches, are widely believed to be aimed at bolstering the authority of leader Kim Jong-il, 67, who reportedly suffered a stroke last August, as he prepares to hand over power to his son.

Yonhap quoted the South Korean minister as saying that recent intelligence concerning Kim could suggest he is experiencing a relapse in his health.

"The military is intensely monitoring [the situation] while bearing in mind the possibilities that Kim's health has degraded," Lee said, citing reports that North Korea recently used an old photo of Kim to fabricate a news story about a recent field inspection.