The report comes after North Korea declared in recent weeks it was stepping away from a nuclear disarmament-for-aid deal and restoring a reactor that made bomb-grade plutonium.

A US envoy went to Pyongyang on Wednesday in a bid to rescue the pact.

'North Korea has replaced a tower crane that propped up the launch pad and is improving the stability of missile fittings such as reinforcing missile supporters,' Dong-a Ilbo newspaper quoted a source as saying.

The government source was also quoted as saying a system to supply missile fuel was being set up and the facility is supposed to help North Korea cut the time it needs to prepare a missile for launch.

The facility was being constructed at the Musudan-ri site, used in previous launches and located on the east coast. The site has been used to test-fire the country's Taepodong-2 multi-stage missile that has a possible range of up to 3,500km to 4,300km.

South Korea's spy agency could not immediately confirm the report.

North Korea last launched the Taepodong-2 in July 2006 but the missile fizzled and destructed a few seconds into flight. -- REUTERS