SEOUL — North Korea’s latest rocket engine test showed "meaningful progress" in its missile capabilities, Seoul said on Monday, as the nuclear-armed state steps up its controversial weapons development programmes.

The North’s leader Kim Jong-Un oversaw the "successful" test of the powerful new rocket engine, state media said on Sunday, in a move apparently timed to coincide with a trip to Asia by new US Secretary State Rex Tillerson.

It was the latest in a series of moves by Pyongyang, which have recently included the firing of four missiles to its east in what it described as practice for an attack on US army bases in Japan.

"The latest test is believed to have made some meaningful progress in engine functions," Seoul’s defence ministry spokesman told reporters.

"But we need more analysis on its exact propulsive power and applicable use," said Lee Jin-Woo.

The North’s last ground test of a high-powered rocket engine -- which can be used in missiles -- was in September last year, and also observed by Kim.

The weekend’s experiment came as the top US diplomat wrapped up his trip to Tokyo, Seoul and Beijing, having declared Washington would drop the "failed" approach of "strategic patience" with Pyongyang.

In Seoul, Tillerson also warned that US military action against Pyongyang was possible.

The North insists that it needs nuclear and missile weapons for self-defence against "hostile forces", including the US and its ally South Korea.

It has conducted five nuclear tests since 2006 -- three under Kim Jong-Un -- and launched a number of missiles as it seeks to develop a weapon capable of reaching the US mainland.

Expert opinions vary on how advanced the North’s missile capabilities are, but most agree it has made significant progress in recent years. — AFP