More detailed info here:
http://articles.timesofindia.indiatimes.com/2012-06-03/flora-fauna/32005485_1_spider-tinsukia-district-upper-assam
Excerpts:
...But whatever the species, it is a highly aggressive spider. It leaps at anything that comes close. Some of the victims claimed the spider latched onto them after biting. If that is so, it needs to be dealt with carefully. The chelicerae and fangs of this critter are quite powerful; but it's too early to declare it a killer spider. In fact, we are yet to test its venom and find out the toxicity," says Dr Saikia.
...
Whatever it is, it is definitely new to the area.
Assam doesn't have venomous spiders, it never had any throughout history, or there would have been some document, text or art that depicted this spider. People wouldn't have panicked like this; they are scared because they have seen something like this for the first time and don't know how to deal with it. They are used to the common house spider, which runs away when you even snap your finger close to it. But this spider attacks if you try to scare it off. Those who were bitten have said that when they tried to shoo it off, it leapt at them and buried its fangs."
If the spider is indeed the black wishbone, which is found in Australia, how did it come all the way to Assam? Or, if it is the funnel-web spider, how did it suddenly appear at a place that is not its usual habitat? These questions have baffled experts. "There is a lot of insect fauna that is still to be discovered. Therefore, this could be a big find. However, what is worrying is the way these arachnids surfaced all of a sudden and started biting everyone around. Its behaviour shows that it is not used to human presence; so, there is some ground to believe that this may have been accidentally or intentionally introduced to our eco-system.