The Hindu nationalist juggernaut of Indian Prime Minister Narendra Modi is for the first time encountering both internal and international resistance.

Emboldened by his re-election by a landslide in a general election held in April and May, Modi has since implemented striking, though somewhat controversial reforms, the latest of which has triggered deadly protests at home and concern abroad with analysts wondering whether he has now overreached.

It concerns a citizenship law that critics say reinforces the notion of India as a Hindu nation with a Hindu-first policy and undermines its secular constitution.

Under the law passed by parliament last week, religious minorities such as Hindus and Christians in neighboring Muslim-majority Bangladesh, Pakistan and Afghanistan who settled in India before 2015 will have a path to citizenship on the grounds that they faced persecution in those countries.

The critics mostly contend that the legislation discriminates against Muslims, who form a sizable minority in India.

Protest rallies have been taking place in several cities, including the capital Delhi, although the reasons for the demonstrations may vary from state to state. Some border communities, for example, fear an influx of new migrants.

UN leads international criticism

Modi had gained widespread backing within the country for previous perceived Hindutva moves this year, such as the revocation of the decades-long status of Muslim-majority Kashmir that gave it special privileges and for making the practice in Islam of "instant divorce" a criminal offense.

The Office of the United Nations High Commissioner for Human Rights has led the international criticism of the nationality law, describing it as "fundamentally discriminatory in nature."

"Although India's broader naturalization laws remain in place, these amendments will have a discriminatory effect on people's access to nationality," Jeremy Laurence, a spokesperson for the UN agency, said.

The United States, generally regarded as an ally of India, has advised caution. "The United States urges India to protect the rights of its religious minorities in keeping with India's constitution and democratic values," a State Department spokesperson said.

The Commission on International Religious Freedom, a U.S. government entity, went further by urging Washington to consider sanctions against Amit Shah, India's interior minister, and other leaders.

Rahul Gandhi, the leader of the main opposition Congress party, accused the Modi government of dividing Indian society through the legislation as well as a plan to launch a national citizenship register. When such a register was tested in the northeastern state of Assam earlier this year with the intention of rooting out undocumented immigrants from Bangladesh, nearly two million people, many of them Muslims, were excluded from the citizenship list.

That omission, apparently for lack of documentary evidence, has helped to fuel some of the anger that is being seen on the streets today.

"We have no problem if you give citizenship to refugees," Congress member of parliament Manish Tewari told a recent public forum. "We want that if you want to give someone citizenship, give it on the basis of compassion and not a religion..."

Government 'prioritizing' political agenda

Government officials have responded that the law is intended to protect persecuted religious minorities in some neighboring countries. They claim it does not include Muslims because they do not need such protection in India.

Modi has defended the move and termed the protests deeply distressing.

"No Indian has anything to worry regarding this act," he said in a tweet. "This act is only for those who have faced years of persecution outside and have no other place to go except India. This is the time to maintain peace, unity and brotherhood."

Michael Kugelman, a South Asia expert at the Woodrow Wilson International Center for Scholars, assessed the situation this way: "I do think that Washington, like most other Western capitals, holds India to a particularly high standard (so) I think there is some genuine surprise and disappointment that the world's largest democracy appears to be undercutting its long-standing and fundamental traditions of secularism, democracy and pluralism."

Kugelman believes that Modi still has most of the country behind him for now and his handling of the economy will be the biggest predictor of his political fate.

Even before the protests began, Ronojoy Sen, a senior research fellow in the South Asian Studies Program of the National University of Singapore, was suggesting in September that the governing Bharatiya Janata Party's political and cultural agenda for its second term had taken precedence over economic concerns. In fact, Modi's election campaign had focused more on issues of national security rather than of bread and butter.

But the economy has been slumping this year, with the rate of growth hitting a six-year low of 4.5 percent in the third quarter. The International Monetary Fund (IMF) has already signaled that it will likely downgrade growth prospects in January.

"It is likely to be a significant downward revision for India," IMF chief economist Gita Gopinath said in Mumbai on Tuesday. The Fund had initially projected that the Indian economy would expand by 7% in 2020.

The protests mean that Modi has one more big problem to deal with as he heads toward the New Year.