SEOUL: The Democratic People's Republic of Korea (DPRK) may test mid-range missiles or fire more short-range missiles to step up sabre rattling that has raised regional tension, a newspaper in the Republic of Korea (ROK) said on Friday.

DPRK fired four short-range missiles on Thursday, which follows a rocket launch in April that boosted its long-range missile capability and a nuclear test on May 25 that put it closer to having a working atomic bomb.

"Their behavior continues to be unpredictable, although the activity we've seen today was not unexpected," Pentagon spokesman Bryan Whitman said.