Seoul, Jan 14 (IANS): North Korea fired an unidentified projectile eastward on Friday, hours after it warned of a "stronger and certain" response following the US' imposition of new sanctions, South Korea's military said.

The Joint Chiefs of Staff (JCS) announced the launch, the third in a little over a week, without elaborating further, reports Yonhap News Agency.

Earlier in the day, Pyongyang issued the warning after Washington slapped the sanctions on six North Koreans involved in the regime's weapons of mass destruction and ballistic missile programmes on Wednesday.

"If the US adopts such a confrontational stance, the DPRK will be forced to take stronger and certain reaction to it," a spokesperson of the North's Foreign Ministry said in a statement carried by the Pyongyang's official Korean Central News Agency.

DPRK stands for the North's official name, the Democratic People's Republic of Korea.

The North fired what it claims to be hypersonic missiles on January 5 and Tuesday, in an apparent quest for new advanced weapons amid a deadlock in nuclear talks with the US.