As US President Donald Trump announced a series of defence deals with India after holding talks with Prime Minister Narendra Modi, the capital New Delhi was rocked by a third day of violence over citizenship protests.

Trump, in a joint news conference with Modi on Tuesday, confirmed earlier reports that India had agreed to buy $3bn worth of military equipment from the United States, including Apache and Romeo MH-60 helicopters.

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As expected, the two right-wing leaders did not announce the much-delayed trade deal between the two countries, with Trump saying he was "optimistic" a comprehensive trade deal will be reached, without providing any further details.

Trump said the US, India, Australia and Japan have "revitalised" a joint security initiative and will expand cooperation on counterterrorism, cybersecurity and maritime security.

The US president also said he and Modi were committed to protecting their citizens from "radical Islamic terrorism" and that, to that end, the US was also working "productively with Pakistan to confront terrorists" that Trump said operated from Pakistani soil.

The two countries had initially planned to produce a "mini deal", but that proved elusive.

"The biggest sticking point between the US and India is trade. They have had serious differences," Al Jazeera's Elizabeth Puranam reported from New Delhi.

She said the two countries went through a year of retaliatory tariffs in 2018 and there was no progress on that.

"That's why the US Trade Representative Robert Lighthizer did not come here ahead of Trump's visit," she added.

The US has signed a trade deal with China and separate agreements with Canada and Mexico and has been pushing for a trade accord with New Delhi, which Trump has in the past described as the "tariff king".

Despite tensions over bilateral agreements, Trump's visit has been a rousing success since he arrived in the western city of Ahmedabad on Monday - receiving a warm welcome by tens of thousands people and addressing a packed stadium for a "Namaste Trump" rally.

"I know that our two nations will continue to achieve new breakthroughs, unlock new potential and forge even brighter futures in the years ahead," Trump told reporters on Tuesday.

"We think we're at a point where our relationship is so special with India, it has never been as good as it is right now," he added.

India is one of the few big countries in the world where Trump's personal approval rating is above 50 percent and Trump's trip has got wall-to-wall coverage with commentators saying he had hit all the right notes on his first official visit to the country.

Violence in New Delhi

While Trump has heaped praise at his host for the warm welcome in Ahmedabad, violent protests that broke out in New Delhi on Sunday over the new citizenship law, known as the Citizenship Amendment Act (CAA), placed Trump's visit to the nation's capital in a more critical light.

"We are seeing here pictures of rioting, shops, cars being set on fire. This is exactly what the Indian government and PM Modi did not want to happen during US President's Trump's visit. It has happened," Puranam reported.

Critics say the new law passed in December discriminates against Muslims and is a further attempt to undermine the secular foundations of India's democracy. They say the law is part of a pattern of divisiveness being followed by Modi's Hindu nationalist Bharatiya Janata Party (BJP).

At least seven people were killed and about 90 were injured in clashes on Monday that took place in the northeast part of the capital, away from the centre of the city where Modi is hosting Trump.