At least two people have died in clashes with Indian police in the north-eastern state of Assam, officials said. Police said the two had been caught in crossfire in the city of Guwahati where thousands had ignored a curfew to protest against a new citizenship bill. Troops have been deployed in parts of Assam and neighbouring Tripura state. The Citizenship Amendment Bill (CAB) offers amnesty to non-Muslim illegal immigrants from three countries. Critics across India say the bill is discriminatory. In the north-east, protesters claim they will be "overrun" by migrants from Bangladesh. Prime Minister Narendra Modi has appealed for calm. The bill - which applies to people from Afghanistan, Bangladesh and Pakistan - was passed in the upper house of parliament on Wednesday night. It is yet to be signed by the president, but that is considered a formality. The ruling Hindu nationalist Bharatiya Janata Party says the CAB will give sanctuary to people fleeing religious persecution. Illegal migration from Bangladesh has long been a concern in India's north-east. Assam is one of India's most multi-ethnic states and includes Bengali- and Assamese-speaking Hindus and various tribespeople. A third of its 32 million citizens are Muslims, the second-highest number after Indian-administered Kashmir.