It's not a claim, but a fact. There are videos documenting the "peace" messengers bitting the hell out of the soldiers with iron poles, stabbing them with knives, throwing soldiers off the deck, stilling their pistols and shooting them. Some of those "peace" activists on the turkish ship were hired by Al Qaeda especially to hurt soldiers and start a bloody fight. This sail had nothing to do with humanitarian aid, but was first and foremost a violent provocation done by radicals. The humanitarian aid on those ships (which was very humble) is being sent to Gaza Strip, which could have been done peacefully on the first place, if that was the real intention of those extremists. Think about it, if they would have let them through (unauthorise entering an autonomic state's border), the next ships to come and enter could have carried tons of weapons and terrorists.
UN aid chief says no warring parties observed Yemen truce (Reuters)
from the article: Activists: We have funding for another larger Gaza flotilla