Prime Minister Narendra Modi sought Sunday to reassure India's Muslims as a wave of deadly protests against a new citizenship law put his Hindu nationalist government under pressure like never before.

At least 25 people have died in almost two weeks of demonstrations and violence after Modi's government passed the law criticised as anti-Muslim. More protests took place on Sunday.

Addressing party supporters in New Delhi — who cried “Modi! Modi!” at the mention of the law — the 69-year-old said Muslims “don't need to worry at all” provided they are genuine Indians.

“Muslims who are sons of the soil and whose ancestors are the children of mother India need not to worry,” Modi told the crowd of thousands.

Accusing the main opposition Congress party of condoning the recent violence by not condemning it, Modi said opponents were “spreading rumours that all Muslims will be sent to detention camps”.

“There are no detention centres. All these stories about detention centres are lies, lies and lies,” he said.

Modi also said that there had been “no discussion” about a nationwide “register of citizens”, which many Muslims in India fear is targeted mainly at them.

Read more: India protests rage against citizenship law, but Modi defiant

Home Minister Amit Shah, Modi's close ally, has said repeatedly that such an exercise will take place, including in parliament aimed at removing all “infiltrators” from India.

This year such a register in Assam state left off 1.9 million people unable to prove they or their forebears were there before 1971. They now face possible statelessness.

Assam has six functional detention centres holding more than 1,000 people in the northeastern state and plans another 11.

The Home Ministry in June issued a “2019 Model Detention Manual” to states, asking them to set up camps in major entry points.

Hindu nation

The demonstrations have been largely peaceful but protesters have also hurled rocks and torched vehicles, while heavy-handed police tactics including the storming of a Delhi university a week ago have fuelled anger.

Tens of thousands of protesters gathered late Saturday in the southern city of Hyderabad. Other protests took place on Sunday, including in Jaipur and Mumbai. Another in favour of the law was held in Bangalore.

The law gives religious minority members — Hindus, Sikhs, Jains, Parsis, Christians and Buddhists — from three neighbouring Islamic countries an easier path to citizenship, but not if they are Muslim.

Islamic groups, the opposition and others at home and abroad fear this forms part of Modi's aim to marginalise India's 200 million Muslims and remould the country as a Hindu nation, something he denies.

Authorities have imposed emergency laws, blocked internet access — a common tactic in India — and shut down shops in sensitive areas across the country in an attempt to contain the unrest.

More than 7,500 people have either been detained under emergency laws or arrested for rioting, according to state officials, with 5,000 in Uttar Pradesh state alone where 17 people have been killed.

Some 500 people have also been injured in Uttar Pradesh including 263 police, while two people were shot dead in the southern state of Karnataka and six died in Assam in the northeast last week.

Read more: Why Guwahati exploded in protests — and what explains Assam's resistance to India's Citizenship Bill

In Assam, opponents of the legislation fear it will enable large numbers of Bengali-speaking immigrants, many of whom are Hindu, to settle there.

But elsewhere, opponents say the law has made religion a test for citizenship ahead of a nationwide register that Modi wants to carry out by 2024 to remove all “infiltrators”.

The US State Department this week urged New Delhi to “protect the rights of its religious minorities in keeping with India's constitution and democratic values”.

Modi's government, re-elected in May, has defended the law saying it is meant to help “persecuted” minorites from Muslim-majority Pakistan, Bangladesh and Afghanistan.