SEOUL, South Korea — South Korea blared propaganda broadcasts into North Korea today after a six-year halt, and Pyongyang said its troops were bracing for war as tensions spiked on the divided peninsula over the sinking of a warship.

One Seoul-based monitoring agency reported that North Korea's leader ordered its 1.2 million-member military to get ready for combat after South Korea blamed the North for a March 26 torpedo strike that sank the warship Cheonan and killed 46 sailors. South Korean officials could not immediately confirm the report.

The South's restarting of psychological warfare operations — including radio broadcasts into the North and placing loudspeakers at the border to blast out propaganda — were among measures the government announced Monday to punish Pyongyang. The South is also slashing trade and denying permission to North Korean cargo ships to pass through South Korean waters.

A team of international investigators concluded last week that a torpedo from a North Korean submarine tore apart the Cheonan. The sinking was one of the South's worst military disasters since the 1950-53 Korean War, which ended with an armistice, not a peace treaty.

The North denies involvement and has warned such retaliation would mean war.