“Our military will not sit idle until warmongers launch a pre-emptive strike,” an unidentified military commentator said in a statement carried by the North’s official Korean Central News Agency. “Everything will be in ashes, not just a sea of fire, once our advanced pre-emptive strike begins.”

The remarks, also carried on state television, marked the third straight day of bellicose rhetoric from North Korea, which is angry over the harsher line new South Korean President Lee Myung-bak has taken against Pyongyang since assuming office last month.

Such tough talk from North Korea is not unusual during times of increased tensions. In 1994, a North Korean official threatened to turn Seoul, located just 50 kilometers (31 miles) from the border, into a “sea of fire.” The North has also used the expression in relation to threatened retaliation against U.S. military bases.

The latest verbal salvo also came just two days before a scheduled visit to South Korea by the chief U.S. negotiator in stalled North Korean nuclear disarmament talks.

South Korea’s Defense Ministry reacted calmly.

A senior military officer at the ministry said officials were working “to ensure the public would not worry about” the North’s recent actions and statements. He declined to elaborate and asked not to be named because he was not authorized to speak to media.

On Friday North Korea test-fired a barrage of ship-to-ship missiles into its western sea and warned that it would “mercilessly wipe out” any South Korean warships that violate its waters near their disputed sea border.

On Saturday, the North warned that inter-Korean reconciliation could be in jeopardy unless Seoul apologizes for the military leader’s comment. It said it would ban South Korean officials from the country, without saying when the ban would begin or how long it would last.

Sunday’s statement also warned that the North would suspend all scheduled inter-Korean dialogue unless Seoul retracts the remark and apologizes.

Kim Tae-young, chairman of the South’s Joint Chiefs of Staff, told a parliamentary hearing Wednesday that the military would strike a suspected North Korean nuclear weapons site if Pyongyang attempted to attack the South with atomic bombs.

Kim’s office said later he was talking about a general military principle dealing with outside threats — not about launching an unprovoked pre-emptive attack on the North.

South Korea’s Defense Ministry reiterated Sunday that it would decide whether to send a response to the North over its demand for a retraction in a few days.

The North Korean military commentator also said that Pyongyang would ban South Korean officials — including military officers — from crossing the border, but gave no details on timing.

“There is a limit to tolerance,” the commentator said.

Since a landmark inter-Korean summit in 2000, South Korean officials have often traveled across the two countries’ heavily fortified border for talks. In October last year, the two countries held their second summit.

On Thursday South Korea withdrew officials from a joint economic office in North Korea at Pyongyang’s request.

North Korea was angry after South Korea’s unification minister said Seoul would hold off on expanding the joint industrial zone until the dispute over Pyongyang’s nuclear programs was resolved.