Hundreds of antiquities valued at $14m have been returned to India by New York authorities, including some connected to the alleged art smuggler Subhash Kapoor, in a move that is likely to raise the pressure on others to make similar gestures.

The return of 657 antiquities was announced by the Manhattan district attorney, Alvin Bragg Jr, on Tuesday, and came as New York City’s mayor, Zohran Mamdani, waded into the historically contentious ownership of the 105.6 carat Koh-i-noor diamond.

Mamdani, the city’s first democratic socialist mayor, suggested to reporters that Britain should return the gem – which is set into the Queen Mother’s crown and held in the Tower of London – to India, hours before shaking hands with King Charles on Wednesday at the 9/11 memorial.

Mamdani’s press office did not mention meeting the British monarch in its daily scheduling Wednesday and later said: “I’ll be attending a wreath-laying alongside a number of other elected officials.”

But Mamdani said that if he met with Charles privately, he “would probably encourage him to return the Koh-i-noor diamond”.

The return of Indian antiquities recovered from several ongoing investigations was held at a ceremony at the consulate general of India. A spokesperson for the prosecutor’s office said the ceremony had been scheduled months earlier and was not connected to the royal visit.

“The scale of the trafficking networks that targeted cultural heritage in India is massive, as demonstrated by the return of more than 600 pieces today,” Bragg said at the ceremony.

“There is unfortunately more work to be done to return stolen artifacts back to India, and I thank our team for their persistent efforts.”

The pieces include a bronze figure of Avalokiteshvara, a Buddhist deity, seated on an inscribed double-lotus base over a lion-flanked throne. It was stolen and smuggled into the US by 1982, ultimately ending up in a private collection in New York by 2014.

Others include a red sandstone figure of a Buddha standing with his right hand raised in a gesture of protection, which was looted from Northern India and smuggled into the US by Kapoor, who is under indictment on smuggling charges. A sandstone figure of a dancing Ganesha looted by an indicted co-conspirator, Ranjeet “Shantoo” Kanwar, was also returned.

Mamdani’s remark opens a can of worms over a gem that has at times been in the possession of the Mughal and Persian empires, as well as many others. Britain acquired the stone in 1849 and it is now a powerful symbol in the debate over colonial history. India, Pakistan, Iran and Afghanistan have all claimed ownership.

A spokesperson for the mayor, who was born in Uganda to parents of Indian origin, told the New York Times that the mayor “is generally opposed to the idea of a king”. Mamdani’s administration has described New York’s history as “one of colonization, exploitation, and racial oppression”.

William Dalrymple, co-author of the 2017 book Koh-I-Noor: The History of the World’s Most Infamous Diamond, told the New York Times that the diamond “has a long history of bringing bad luck and, again, seems to have been the tripwire which tripped up King Charles on his trip to New York”.