The reason for these measures is the tax dispute between Nokia and the Indian government, which has not been resolved yet. Last year, the Indian officials stated that the smartphone maker hadn't paid the whopping amount of $3 billion in taxes and froze all assets of the company, including the Chennai plant itself.
The government demanded that Nokia should pay roughly $500 million if it wants to see its property returned. Nokia stated that the government's claims are simply “absurd” and denied to pay. According to analysts, the Chennai plant in India is a valuable asset, worth at least $1 billion to Nokia. Its closedown might affect the merger with Microsoft in a very bad way.
Apparently, Nokia workers across India were not very happy with these recent developments, as they went on a one-day strike and local Chennai employees even went on a hunger strike on April 1. It seems that most of them will have to find another job, yet it's positive to see that the Finnish giant is trying to take care of its workers.
source: The Hindu Business Line via WMPoweruser