SEOUL, South Korea - North Korea warned Monday that it does not engage in "empty talk" and has "guns and bayonets" aimed at its southern neighbor, heightening tensions surrounding its threat to take military action to counter what it calls South Korean plans to invade.

But South Korean President Lee Myung-bak made clear that he won't bend to the North's saber-rattling. On Monday, he named a security expert hawkish on Pyongyang as his unification minister in charge of relations with the communist neighbor.

Like the president, Hyun In-taek is a strong critic of the "Sunshine Policy" espoused by Lee's two liberal predecessors, who sought to pave the way for reconciliation by offering the North unconditional aid.

Analysts say Hyun's appointment suggests Lee will stick to his hard-line policy on the North.

"I'll make efforts to back the president's philosophy and policy so as to move the South-North relations forward," Hyun told The Associated Press. He did not elaborate and declined to comment on views that he is a hard-liner.

Over the weekend, North Korea's military accused South Korean President Lee Myung-bak of plotting an invasion of the North and warned of strong military steps in retaliation and "an all-out confrontational posture." South Korea denied it was planning to invade and put its military on alert.

South Korea said Monday it had detected no unusual moves by the North's military, and Unification Ministry spokesman Kim Ho-nyeon said Seoul will cope with the situation in a "calm" manner.

Tensions between the two Koreas, which technically remain at war because their 1950-53 conflict ended in a truce, not a peace treaty, have been escalating since Lee took office nearly a year ago pledging to get tough with the nuclear-armed neighbor. The North since has cut off all ties and suspended several joint projects.

The North's main Rodong Sinmun newspaper renewed the country's warnings Monday, saying it would "destroy and wipe out" invaders in "one strike" if South Korean "war maniacs ignite the fire of war."

"The Lee Myung-bak group should bear in mind that our guns and bayonets ... are aimed at their throats," the paper said in a commentary, carried by the official Korean Central News Agency. "We know no empty talk."

Such threats are not uncommon and are typically issued through state-run media. Saturday's threats, however, were read by a uniformed army officer flanked by military flags -- the first time since 1998 an officer has served as messenger rather than state media, according to South Korean officials.

Despite the threats, South Korea's No. 2 nuclear negotiator led a team of experts on a five-day trip to North Korea -- Seoul's highest-level visit in a year and a sign Pyongyang has not abandoned an international 2007 disarmament-for-aid pact that has been stalled since August.

Envoy Hwang Joon-kook said Monday that the team toured nuclear facilities at the North's main reactor at Yongbyon and met with Foreign Ministry officials. "It seems like their stance (on the nuclear process) is mostly unchanged," he told reporters as he arrived in Beijing from Pyongyang.

Analysts say the North's latest saber rattling also is a negotiating tactic aimed at Seoul and Washington ahead of President-elect Barack Obama's inauguration Tuesday.

"North Korea wants to draw Obama's attention," said Kim Yong-hyun, a professor at Seoul's Dongguk University. He said Pyongyang wants to use the tensions with Seoul to make a case for its long-standing demand for diplomatic ties with Washington -- the regime's top foreign policy goal.