North Korea test-fired a short-range missile off its west coast last week in the first such launch for 19 months, South Korean sources said Wednesday.

The launch was seen as a routine test to improve the country's missile capability, the sources said, declining to give details. The defence ministry had no comment.

Yonhap news agency quoted an intelligence source as saying that the North fired the KN-06 missile into the Yellow Sea in the middle of last week, apparently to test efforts to increase its range.

JoongAng Ilbo newspaper also reported a launch of the KN-06, which has a range of 100-110 km (62-68 miles).

It quoted a Seoul military official as saying the launch appeared to have been planned before a series of threats against South Korea last week from the hardline communist state.

It was the North's first known test of short-range missiles since October 2009, when it test-fired five KN-02 surface-to-surface missiles off its east coast.

Pyongyang in the past has often scheduled such launches for political effect.

Tensions on the peninsula are high following two deadly border incidents last year which Seoul blames on its neighbour.

On May 30 the North announced it would no longer deal with the South's conservative government.

And last Friday its military threatened retaliation unless Seoul punishes troops who used pictures of Pyongyang's ruling dynasty as rifle-range targets.