NEW DELHI - India's parliament was thrown into disarray Tuesday as opposition lawmakers protested at mass conversions to Hinduism, with the uproar threatening to disrupt Prime Minister Narendra Modi's legislative agenda.

Angry lawmakers stormed the well of parliament's upper house forcing its shutdown for the day. They demanded Modi make a statement on reports of poor Muslims being coerced into converting to India's majority religion. "The house will not run until the prime minister comes for discussion over the communal incidents and forced conversions issue," Derek O'Brien, from the regional opposition All India Trinamool Congress, told reporters.

The warning threatens to disrupt the Modi government's plans to pass a series of major economic reforms through parliament, with just four days of the current session remaining. The right-wing government, which swept to power at national elections in May on a pledge to reform and revive the economy, wants to pass a bill to open the insurance sector to foreign investment.

The government was also inching closer to finalising agreement with India's states on taxation reform by introducing a national sales tax, according to local media reports on Tuesday. Finance Minister Arun Jaitley was hopeful of tabling a constitutional amendment in the current parliament for introduction of the long-awaited goods and services tax (GST), to replace a myriad of overlapping state duties that deter investment.

A hardline group linked to Modi's Hindu nationalist Bharatiya Janata Party (BJP) has been accused of converting some 50 slum-dwelling Muslim families last week in the Taj Mahal city of Agra.  One of the converts told AFP they were promised ration cards and other financial incentives if they went ahead with the conversions.

A BJP lawmaker has since announced plans for an even biggger conversion event of Christians and Muslims on Christmas Day in the northern town of Aligarh.

Critics say Hindu hardline groups have become more emboldened since the BJP was elected, with rising communal tensions in the Hindu-majority but multi-faith country. Parliament under the previous Congress-led government was routinely paralysed, with shouting, jeering and protests frequently forcing adjournments.

Modi's BJP won the biggest mandate in 30 years in May, raising hopes it would have the numbers to control parliament and ensure the smooth passage of legislation.

But the BJP lacks a majority in the upper house, where Congress and regional lawmakers have combined to protest at a range of issues.

Meanwhile, India on Tuesday declared a ban on Islamic State, days after having detained an engineer for running a popular Twitter account extolling the militant group's military campaign. India has the world's third-largest population of Muslims, but they have largely shunned Islamist causes. Police say only four Indians are known to have joined Islamic State, and one has since returned and is in custody.

Until now, India had held off on a ban on Islamic State, because of the group's lack of activity in the country and worries over the fate of 39 Indian construction workers missing in Iraq this year, who are believed to be held by the group. Officials had also suggested it would be harder to track sympathizers if the group was banned, driving them towards covert activity.

Home Minister Rajnath Singh told parliament the government aimed to limit the activities of the Middle Eastern group which has carved out swathes of territory in Iraq and Syria. "We had taken cognizance of Islamic State in Iraq and Syria activities in other countries," he said. "As a first step we have banned this outfit in India."

On Saturday, police picked up Mehdi Masoor Biswas, a 24-year-old food company executive from the southern tech hub of Bengaluru, saying he was running the pro-Islamic State Twitter handle @ShamiWitness that had 17,800 followers, including hundreds of foreign fighters for the group.

Police were poring over 129,000 tweets he had posted over several years to determine if he was simply a cheerleader for the group or an online recruiter, an officer said.

"It is true the number of Indians in the group or involved in its activities is only a handful," Singh said. "But I want to make clear we are taking this seriously."

A ban on the group makes it easier for police to prosecute suspects, an aide said.

Officials had feared a ban on Islamic State could endanger the lives of 39 men believed to be held by the group since June. There has been no word yet on the fate of the workers.