North Korea on Wednesday threatened to destroy Seoul and the South Korean presidential office if there is any sign of pre-emptive strikes by the United States and the South against Pyongyang.

Rodong Sinmun, the North's main newspaper, said that the country will strengthen its nuclear capabilities in quantity and quality in response to what it called its enemies' scheme for aggression.

"We have warned that South Korea will be engulfed in a sea of fire and the US military units in the Pacific region and the mainland will be in chaos if the US wages nuclear strikes against us," the newspaper said. "Our warning is not an empty word."

North Korea has further ratcheted up war rhetoric since speculation has spawned that the US may consider pre-emptive strikes against the North over Pyongyang's nuclear and missile programs.

In September, an independent task force report from the Council on Foreign Relations, suggested that Washington, Seoul and Tokyo should send a strong message to the North that future aggression will meet strong responses, including "strikes against military targets inside North Korea."

South Korea said it has not had any discussions with the US over a possible pre-emptive strike on the North.

North Korea conducted its fifth and most powerful nuclear test in September, eight months after its fourth nuclear test. The United Nations Security Council is working on a fresh sanctions resolution to punish it for the latest nuclear provocation.

Meanwhile, the North's main propaganda website Uriminzokkiri unveiled video footage in which the North placed photos of the White House and Cheong Wae Dae, South Korea's presidential office in the crosshairs.