* Govt forces would struggle against battle-hardened militias
* North Korean-flagged tanker seized by govt forces - minister
* Oil blockade has slashed vital govt revenues (Adds government forces seizing tanker, paragraphs 4-7)
By Ulf Laessing and Feras Bosalum
TRIPOLI, March 10 (Reuters) - Libya's parliament has ordered a special force to be sent within one week to "liberate" all rebel...