North Korea will attack South Korean capital Seoul and the presidential office located in the city, the isolated nation’s main newspaper Rodon Sinmum warned Wednesday. The threat comes amid the North’s fears of preemptive strikes by U.S. and South Korea against Pyongyang.

“We have warned that South Korea will be engulfed in a sea of fire and the U.S. military units in the Pacific region and the mainland will be in chaos if the U.S. wages nuclear strikes against us,” the newspaper said, according to Yonhap News Agency. “Our warning is not an empty word.”

The daily further added that the Kim Jong Un-led country will fortify its nuclear capabilities in response to what it called its enemies’ scheme for aggression, Yonhap reported.

North Korea has been worried about preemptive strikes by Washington and Seoul since the allies have stepped up their military drills in the Korean Peninsula. Earlier this month, Washington and Seoul conducted naval drills as a show of force against North Korea. The allies, along with the U.K., will be carrying out military drills ‘Invincible Shield’ against Pyongyang in November. The reclusive state has called the upcoming exercise a “hostile act” and asked the U.K. to pull out from the drills.

Meanwhile, North Korea’s intermediate ballistic missile program is likely to go operational next year, according to 38 North. On Saturday, Pyongyang had failed missile test near Kusong city in the northwestern part of North Korea.

“Moving to a roadside near Kusong is like taking the training wheels off the bicycle, seeing if you really have mastered something new,” 38 North reported. “They are continuing with an aggressive test schedule that involves, at least, this time, demonstrating new operational capabilities. That increases the probability of individual tests failing, but it means they will learn more with each test.”

The missiles are expected to be operational “sometime next year” — well ahead of the expected schedule, the report added.