The U.S.-South Korea joint military drill ended on Tuesday officially, although South Korea is still closely monitoring the north for signs of aggression, Seoul’s defense ministry said.

The two-month annual exercise, known as “Foal Eagle,” which began on March 1, shortly after North Korea carried out its Feb. 12 nuclear test, had been a source of displeasure for Pyongyang.

The exercise involved more than 10,000 U.S. troops and  with a much larger number of South Korean personnel.

“The drill is over but the South Korean and U.S. militaries will continue to watch out for potential provocations by the North, including a missile launch,” South Korea's defense ministry spokesman Kim Min-seok told reporters, according to the AFP.

“We [believe] the exercise had ... a great outcome. Also, this training was led by the South Korean military, so it was a good chance to examine [the] South Korean army's capability,” he added.

Pyongyang began ratcheting up tensions by announcing in early March that it had nullified the 60-year-old armistice agreement that ended the Korean War, although technically the pact does not allow unilateral nullification.

On Monday, North Korea's Rodong Sinmun newspaper described “Foal Eagle” as “attack rehearsals” that were “driving the situation of the Korean Peninsula to a nuclear war.”

Japan's Asahi Shimbun newspaper on Monday reported that North Korea has stopped sending signals from its wireless telemetry system , which is designed to record missile flights and ground-based radar stations, since April 20.

South Korean military officials said the signals have been spotted intermittently and that they are monitoring Pyongyang’s latest activities, while maintaining high military readiness, Seoul’s Yonhap news agency reported.

“Signals have been on and off, but the situation comes to an end only when [the North] withdraws [its missiles],” defense ministry spokesman Kim Min-seok said in a daily briefing. “It is hard to grasp the North's intention whether it is for real or for manipulation.”

Earlier, South Korean intelligence authorities said that Pyongyang, in early April, moved two mid-range Musudan missiles to Wonsan, on the eastern coast of North Korea, opposite Pyongyang, and placed seven mobile missile transporter-erector-launchers in Wonsan and South Hamgyeong Province, also on the eastern coast.

Satellite imagery released after April 16 showed that two additional launchers for short-range Scud missiles were moved to South Hamgyeong Province, according to reports from South Korea.