Afghan President Hamid Karzai on Monday accused a Pakistan-based militant group of being behind last week's attack by gunmen on an Indian diplomatic mission in the west of his war-torn country.

On the eve of talks between India's new Prime Minister Narendra Modi and his Pakistani counterpart Nawaz Sharif, Karzai blamed Lashkar-e-Taiba for Friday's attack on the consulate in Herat, the latest in a string of assaults on Indian targets in Afghanistan.

U.S. President Barack Obama congratulated Narendra Modi and said he was looking forward to working with him after he was sworn in as Indian prime minister on Monday.

"As the president and prime minister agreed in their call after the election, as the world’s two largest democracies, India and the United States share a deep bond and commitment to promoting economic opportunity, freedom, and security for our people and around the world," a White House statement said.

India's Narendra Modi was sworn in as prime minister Monday holding the strongest mandate for 30 years, promising to forge a "strong and inclusive" country on a first day that signaled his bold intentions.

The 63-year-old Hindu nationalist broke with tradition and invited his Pakistani counterpart Nawaz Sharif who arrived at the ceremony hailing a "great moment and a great opportunity" for peace in the region.

Indian police fired tear gas to break up clashes between Hindu and Muslim mobs in Narendra Modi's heartland of Gujarat on the eve of his swearing in as prime minister, officials said Monday.

Angry crowds set fire to several shops and vehicles and pelted stones at each other during the clashes in western Gujarat state's main city of Ahmedabad on Sunday night, police and fire officials said.

A passenger express slammed into a stationary freight train in northern India killing at least nine people on Monday, as rescuers worked frantically to free those trapped inside mangled carriages, officials said.

The express was travelling to Gorakhpur city in northern Uttar Pradesh state when it collided with the stationary train at a local station mid-morning, leaving scores of passengers injured, officials said.

Pakistan Prime Minister Nawaz Sharif arrived in New Delhi on Monday for the swearing-in ceremony of his incoming Indian counterpart Narendra Modi in a symbolic meeting of the two regional rivals.

Sharif smiled and waved to television cameras after landing at the capital's main airport, where he was greeted by Indian dignitaries and given a bouquet, ahead of the ceremony later Monday.

Narendra Modi will be sworn in as India's prime minister Monday, with the pro-business leader already signaling bold intentions by slashing his cabinet and welcoming his Pakistani counterpart to the ceremony.

After a decade of left-leaning Congress party rule, the 63-year-old Hindu nationalist is set to steer India firmly to the right in the next five years, armed with a powerful mandate after a landslide election victory.

Pakistan's Prime Minister Nawaz Sharif on Sunday ordered the release of 151 Indian prisoners ahead of his historic visit to New Delhi to attend Narendra Modi's swearing-in as premier. 

Islamabad's move to free the prisoners -- mostly fishermen accused of violating Pakistan's territorial waters -- was welcomed by India as a diplomatic gesture ahead of the inauguration Monday.

A Canadian businessman was sentenced Friday to three years in prison for bribing two Air India executives and an Indian cabinet minister in a failed bid-rigging scheme.

Nazir Karigar, 67, is the first person to be convicted under Canada's Corruption of Foreign Public Officials Act, which had previously been used to prosecute corporations.

A politician close to India's incoming prime minister Narendra Modi called Thursday for strong relations with the United States after speculation he could bear a grudge over past treatment.

Sudhanshu Trivedi, national spokesperson for Modi's Bharatiya Janata Party that won a resounding victory in recent elections, said there had also been "many apprehensions" about the Hindu nationalist BJP before it last took power in 1998.