North Korea is preparing to launch a large-scale artillery drill on a replica of the South Korean presidential office Cheong Wa Dae in a move to fan cross-border tension in the runup to a rare congress of its ruling party, the military here said Wednesday.

About 30 artillery pieces have been brought to a training range just outside Pyongyang where the replica of Cheong Wa Dae was set up in early April, a Joint Chiefs of Staff official said. 

"The North is likely to conduct an actual exercise in the near future," the official said.

The move is intended to instill animosity among North Koreans toward Seoul's leadership and to tighten internal unity ahead of the congress of the Workers' Party of Korea set to start on May 6, he noted. 

In a series of warlike rhetoric, the North has repeatedly threatened to launch strikes on the presidential office and South Korean state agencies. (Yonhap)