Tamil Tigers

Are the Tamil Tigers in Sri Lanka a terrorist group, guerrilla fighters, or insurgents? I have always thought they were terrorists, but after reading an article found on Reuters at http://www.reuters.com/article/latestCrisis/idUSCOL560, I am less convinced. The author of the article stated that Sri Lankan troops have recently captured a portion of rebel-held territory in Sri Lanka and killed over 30 Tigers in open military confrontations. According to the article, the Tamil Tigers want to create an independent state in north and east Sri Lanka. Because the Tigers are fighting for territory in Sri Lanka in organized military units, wouldn't they be considered guerrilla fighters? Do the Tigers use a lot of propaganda, and if so, would they be considered insurgents? I don't know that much about the Tamil Tigers, so comments about their organization would be interesting. Any ideas?