From that picture of OBL and Manhattan- it looks to me like at least 9 nukes. Do you think that could be possible??? Wouldn't that be overkill? Maybe some of the mushroom clouds really depict other types of explosions?
Could be simple pipe bombs. All the internet is supposing nuclear bombs. But perhaps the attacks are more along their usual lines of bombs in cars or backpacks. Perhaps they are smaller bombs that are "dirty", chemical or have viruses in them.