North Korea seems to have lifted its highest combat alert issued in March and withdrawn two mid-range missiles from its east coast, a senior South Korean source told the Yonhap news agency Tuesday.

Escalating tensions on the Korean Peninsula with constant bellicose rhetoric and actions, Pyongyang on March 26 put its missile and artillery units on the highest alert level, citing the need to protect its sovereignty against threats from South Korea and the United States.

The artillery units target the U.S. mainland, Hawaii and Guam and other U.S. military bases in the Pacific as well as South Korea, according to the statement by the North's military carried by the official Korean Central News Agency.

"North Korea appears to have lifted the highest combat alert around April 30," said the South Korean source, requesting anonymity.

Pulling back two mid-range Musudan missiles the North placed on its east coast went along with relaxing the combat posture, he added.

"It appears that the two Musudan missiles have been moved to some other place, though we have yet to confirm where they are located," the source said. "Intelligence authorities of South Korea and the U.S. are closely tracking them."

The news that the missiles had been moved back came on the eve of a summit in Washington between the U.S. and South Korean presidents.

Park Geun-hye is to hold talks with Barack Obama Tuesday, with the two expected to reiterate the countries' strong alliance. Park, who took office in February, will also address Congress on Wednesday.

But a senior U.S. official from the National Security Council warned that, given the North's unpredictable behavior, it was "premature to celebrate it as good news," the BBC reported.

Pentagon spokesman George Little, who declined to comment directly on the missiles' reported removal, told reporters "what we have seen recently is a provocation pause. And we think that's obviously beneficial to efforts to ensure we have peace and stability on the Korean Peninsula."