North Korea has developed new multiple rocket-launchers with an effective range of 170 kilometres (100 miles), based on Chinese and Russian technology, a report said Wednesday.

The new weapons are capable of firing three-metre (10-foot) rockets guided by a Russian GPS device, Seoul's JoongAng Ilbo newspaper reported.

It quoted an unidentified high-ranking official as saying the North has also introduced Chinese technology to upgrade its mainstream multiple rocket-launchers with a maximum range of 90 kilometres.

The South's defence ministry declined to confirm the report.

The newspaper said the new 170-kilometre rocket-launchers could hit new US military bases under construction in Pyeongtaek, some 65 kilometres south of Seoul.

The US bases 28,500 troops in the South and is planning to move its military headquarters from Seoul to Pyeongtaek.

The South regards the North's multiple-rocket launchers deployed along the border as a serious security threat because they could mount a concentrated attack on Seoul, only 40 kilometres from the border.

Residents in Seoul and neighbouring satellite cities, together home to nearly half the South's 49 million people, have always lived under threat of attack from the North's rockets and long-range artillery.