Tens of thousands of North Koreans gathered in Pyongyang's central square on Friday to protest South Korea's government, which has been sharply critical of the North's failed rocket launch last week.

State television footage showed a massive crowd of soldiers and civilians waving their fists and chanting slogans against South Korean President Lee Myung-bak, as a giant picture stood in the middle of the crowd depicting the leader's throat being slit.

North Korea has threatened to wage a “sacred war” against President Lee's government unless he apologizes for suggesting last week that Pyongyang would rather spend millions of dollars on weapons than on food for its poverty-stricken population.

On Thursday, the North's official Korean Central News Agency quoted space agency officials as saying Pyongyang will continue to launch the satellites “one after another,” disregarding international condemnation of its failed launch.

The defiant statement said scientists have already discovered what caused the rocket to fail barely a minute into its flight last Friday. It did not give a time frame for its next rocket launch.

The United Nations Security Council has strongly condemned the launch and threatened further sanctions, saying the move violated resolutions barring North Korean use of ballistic missile technology.

North Korea says the rocket launches are only intended to launch weather satellites into orbit, which it says are needed for economic development. Critics say the launches are thinly disguised ballistic missile tests.

This week in New York, U.S. ambassador to the United Nations Susan Rice said the world body stands ready to take further action if North Korea persists in its actions.

Earlier this month, South Korean officials released satellite intelligence photos showing new activity at the site of North Korea's two previous underground nuclear tests, raising fears that a third test may be planned.