North Korea's leader may have put off carrying out a mock attack on South Korea's presidential office, right after the country concluded its rare ruling party congress, intelligence sources here said Sunday.

Seoul had warned ahead of the four daylong Workers' Party of Korea event that ended Monday that there was a chance that North Korea could show off an artillery attack on a mock-up of Cheong Wa Dae.

South Korean intelligence confirmed that the North built a scaled-down replica of the presidential office at its Daewon-ri training range just outside of Pyongyang and has moved various artillery pieces to the area. It said that some 50 artillery pieces, including 122 millimeter multiple launch rocket systems and towed howitzers, have been positioned a kilometer away and are ready to turn the building to rubble.

"The North seems to be pulling out its troops and equipment from the firing range after the congress," said an insider, who declined to be identified. "We are trying to determine if the North has opted to cancel the attack or just postponed it."

He said that because the Cheong Wa Dae replica has not been dismantled, it is still possible that Pyongyang just pushed back its drill to better gauge the current situation surrounding the Korean Peninsula.

"The military is keeping close track of Kim's moves and those of its armed forces," the source said. He said the government is trying to determine if the North may have switched from its previous tactic of fueling provocations to concentrating more on improving the livelihoods of ordinary people.

Related to the latest development, a North Korean watcher said with most South Korean media having reported the possibility of the drill in advance, the Pyongyang leadership may have thought they lost the "surprise factor" in conducting such a provocation.

"If the mock attack was put on hold, the order could only have come down from the country's leader Kim Jong-un," he speculated.

In the weeks leading up to the congress, the North made several threats to destroy Cheong Wa Dae.

Kim, while proclaiming the North a nuclear power, had at the same time called for military dialogue with the South, although both Seoul and Washington have brushed off the overture as lacking sincerity. The allies instead called for the country to fulfill its past denuclearization pledge.

The North conducted it first nuclear test in 2006, followed by other tests in 2009 and 2013. The latest underground test carried out in January caused the United Nations Security Council to slap its toughest sanctions yet on the North. (Yonhap)