The two women journalists Euna Lee, a Korean-American, and Laura Ling, a Chinese-American, were arrested two weeks ago after straying across North Korea's northwestern border with China while on assignment.
They now appear to be caught up in the middle of a high-stakes game of 'diplomatic blackmail' as tensions rise over North Korea's plans to conduct a missile-test in defiance of UN resolutions.
Satellite images have shown that a three-stage Taepodong-2 rocket has been installed on a launch pad in preparation for what Pyongyang has called a 'satellite' test, which it will conduct as early as this Saturday.
RSF said it had also received information that contradicted North Korea's earlier claims that the reporters, who work for the California-based Current TV, had crossed into North Korea illegally.
Citing unnamed 'sources' on the Chinese side of the frontier, which is marked by the narrow Tumen River which is frozen at this time of year, RSF said that North Korean border guards had probably crossed into Chinese territory to arrest the pair.
The US is currently working through Swedish intermediaries to secure the journalists' release but RSF has called on China - Pyongyang's only ally in the region - to apply more pressure.