South Korean and the United States military authorities have stepped up monitoring and surveillance on North Korea amid speculation of Pyongyang’s possible provocation around Tuesday.

A military official in Seoul said Sunday that there is no sign that the North's provocation is imminent, but some activities have been detected from the North's missile facilities and bases and thus the military is maintaining a heightened readiness posture and surveillance.

The official said that U.S. Forces Korea has enhanced the operations of the U-2S ultra-high altitude reconnaissance aircraft and South Korea also increased surveillance with the RC-800 and RF-16 reconnaissance planes, the E-737 airborne early warning and control aircraft and P-3C maritime patrol aircraft.

An Aegis destroyer equipped with advanced radar SPY-1D is deployed in the East Sea and the land-based Green Pine missile defense radar is also running to detect ballistic missiles from North Korea.