North Korea said Monday that it successfully test-fired an intermediate-range ballistic missile the previous day which it says can carry a heavy nuclear warhead, claiming that the US mainland is within its striking range.

Pak Jong-hak, the director of Asian affairs, told the diplomats stationed in Pyongyang that the North is ready to counter Washington's possible attacks, according to the Korean Central News Agency.

"Until the US and its followers make a right choice, we will further produce sophisticated and diversified nuclear weapons and striking means and push to prepare for necessary tests," Pak was quoted as saying by the KCNA.

His remarks are seen as hinting at another nuclear explosion or a test of an intercontinental ballistic missile under development.

The missile launched on Sunday appeared to be the most powerful one that the North has ever fired, prompting North Korea to move one step closer to the ICBM development.

North Korean leader Kim Jong-un said in January that his country has entered the final stage of preparing to launch an ICBM. But outside experts said Pyongyang seems to be still years away from doing so. (Yonhap)