SEOUL - The Republic of?Korea's Defense Ministry said Tuesday that all military forces of the Democratic People's Republic of Korea had been placed on high alert in protest against a scheduled joint maritime drills involving a US aircraft carrier.

"It is estimated that the DPRK's emergency order of mobilizing posture is in line with its condemnation of the US aircraft carrier's entrance (to the?ROK's port city) and the subsequent response to it,"??the ROK's Defense Ministry spokesman Kim Min-seok told a press briefing.

Earlier on Tuesday, the DPRK's General Staff of the Korean People's Army said in a statement carried by the Korean Central News Agency that all DPRK troops had been ordered to maintain mobilizing posture, which enables all military forces to be mobilized for operations at any time.

The DPRK's instruction came in protest against the joint maritime drills among the ROK, the US and Japan off the southern coast of the Korean Peninsula. It would involve the nuclear-powered US aircraft carrier USS George Washington, which entered the?ROK's port city of Busan last week.

The military exercise, which Seoul and Washington claimed would enhance capabilities for search and rescue of private ships, was originally scheduled to be staged for three days from Tuesday, but it was delayed for at least two days due to bad weather, spokesman Kim said.

Tensions escalated on the Korean Peninsula after the DPRK unilaterally delayed family reunions for those separated by the 1950-53 Korean War last month. Pyongyang repeatedly slammed?the ROK's?President Park Geun-hye by name recently.

The DPRK also directly slated US Secretary of State John Kerry. In the statement, it said that remarks of high-ranking officials of US President Barack Obama's administration, such as those of the secretary of state proved to be sheer lies, citing Kerry's comments that the United States had no intention to attack the DPRK.

Defense chiefs of Seoul and Washington signed a new joint military strategy last week that will allow the allies to take preemptive strikes against possible threats of the DPRK's nuclear weapons.