The United States says it has thwarted an assassination attempt on an American resident of New York who was supporting the Sikh separatist state. Indian national Nikhil Gupta was indicted on Wednesday on charges of murder-for hire. According to the indictment, the order was allegedly given by an Indian government official. This government official has not been named or charged. The Justice Department's indictment also does not name the targeted individuals. However, US media reported that the target was Gurpatwant Singh Pannun, a dual US-Canadian citizen and member of a US-based Sikh activist group. Sikhs are a religious minority comprising approximately 2% of India's population. Some groups have long called for Sikhs to seek a separate homeland. The White House said it had raised the alleged plot with the Indian government at the most senior levels, adding that Indian officials responded with "surprise and concern". The Indian government earlier said it had started an investigation of security concerns aired by the US in relation to the plot. After the indictment was unsealed, it reiterated this and said relevant departments were examining the issue. According to the indictment, Mr Gupta was involved in international narcotics and weapons trafficking before he was allegedly recruited by an Indian government official in May to pursue the assassination scheme. It alleges Mr Gupta was directed by the official to contact an associate in the US about the plans. Mr Gupta, it says, had intended to meet a hitman who could murder his target in New York City. Instead, the indictment says, he was introduced to an undercover law enforcement officer who said he would assassinate the target for $100,000 (£79,000). Mr Gupta paid $15,000 upfront via an associate on 9 June, according to the indictment, which included an apparent photograph of this exchange. Authorities in the Czech Republic then arrested Mr Gupta on 30 June shortly after US prosecutors released an initial indictment against him. They are still detaining him at the US's request, according to court documents. Court documents say the target was also an associate of Hardeep Singh Nijjar, another leader in the Sikh independence movement who lived outside of India. Mr Nijjar was murdered by masked gunmen outside a Sikh temple in Canada on 18 June which has led to tense diplomatic ties between India and Canada. Canadian Foreign Minister Melanie Joly on Wednesday declined to comment on the US indictment. But speaking to reporters in Brussels, she said Canada stands by its own "credible allegations" that Indian agents were involved in the shooting of Mr Nijjar.