North Korea has been conducting ballistic missile launching drills on a regular basis to counter what it called the United States' nuclear war threats, Pyongyang's state media said Friday.

In its first reference to the country regularly launching missiles, North Korea is seen as hinting that it could conduct missile provocations down the road.

"It was a normal drill that was aimed at countering nuclear war maneuvers staged by enemy forces including the US," said the Rodong Sinmun, the country's main newspaper, referring to the country's firing of four ballistic missiles on March 6.

"Our strategic force is conducting a ballistic rocket launching drill on a regular basis," it added.

North Korea said that it launched four ballistic missiles in an exercise targeting US military bases in Japan, vowing to bolster its missile capabilities in terms of quantity and quality.

Seoul and Washington are carrying out their annual joint military drills with the computer-based war game Key Resolve ending its two-week run on Friday. The two-month Foal Eagle combat training exercise kicked off March 1.

North Korea denounced the exercises as rehearsals for a northern invasion despite Seoul and Washington's assurance that they were defensive in nature.

Analysts said that North Korea may conduct provocative acts around key anniversaries in April including the 105th birthday of late founder Kim Il-sung on April 15. The Korean People's Army marks the 85th anniversary of its creation on April 25.

"By claiming missile launches as regular military drills, North Korea seems aimed at diverting international condemnation against its nuclear and missile programs," said Kim Dong-yub, a professor at the Institute for Far Eastern Studies in Kyungnam University. (Yonhap)