The Munhwa Ilbo newspaper, quoting unnamed senior government officials, said the country had succeeded in test-firing a cruise missile with a 1,000 kilometre (620-mile) range.
"The missile precisely hit the targeted zone, five meters in diameter, during the test launch," an unnamed official was quoted as saying.
The missile had to shuttle 25 times between a launch site and a target around 40 kilometres away before hitting it to replicate the long distance range, another official told the paper.
Defence ministry officials refused to confirm the report.
South Korea has vowed to step up efforts to develop missiles that can launch surgical attacks on missile launching sites deep inside North Korea since its declared nuclear test on October 9.
The new missile can reach all of North Korea as well as Beijing and Tokyo. The unnamed official said Seoul was also developing cruise missile with a range of 1,500 kilometres.
South Korea's media reported last month the country had successfully developed its first cruise missile with a 500-kilometer range. Seoul's defence officials declined to confirm the reports.
The new missile, tentatively named "Cheon Ryong" or Sky Dragon and similar to the US-made Tomahawk, will be deployed for operations by the end of the year, Yonhap news agency said Tuesday.
A US-South Korean defence accord imposes a maximum range of 300 kilometres for Seoul's missiles, in compliance with international arms control efforts.
But South Korean officials believe the agreement applies only to ballistic and not cruise missiles, according to media reports.
The North deploys Scuds and Rodongs with a range of 1,300 kilometres, capable of hitting anywhere in the South, and is developing a Taepodong missile with an expected final range of up to 6,000 kilometres.

Copyright AFP (Agence France-Presse), 2006