MOSCOW (NYTIMES) - In a propaganda video released last year, an ISIS militant wearing a black bandanna and cradling a sniper rifle made the usual grim threats against the US Now, there may be a new twist to his warnings.

The militant, Gulmurod Khalimov, a former police commander from Tajikistan, boasted of his extensive US military training - truthfully, it turns out. But some news accounts say he was subsequently promoted to military commander of the Islamic State in Iraq and Syria.

"I was in America three times," Khalimov said in the video, which appeared online last year. "God willing, I will come with this weapon to your cities, to your homes, and we will kill you."

That prospect remains highly unlikely. But there is no doubt that as he rose in the ranks of a special police force in Tajikistan, a former Soviet republic, Khalimov received extensive taxpayer-funded military training from the US to help counter drug-running and extremism along the border with Afghanistan.

Now, Khalimov appears to have become the second senior commander of the Islamic State, the terrorist group he defected to last year, to have benefited from US military training provided to former Soviet states.

Khalimov's precise rank is unclear; he could be the group's so-called minister of war, or military commander in chief. In any case, the State Department, which oversaw his training, thinks he is important enough that on Aug 30, it offered a US$3 million (S$4.2 million) reward for information on his whereabouts. The ISIS's previous military commander was killed in an airstrike earlier this year.

The State Department has been publicising the reward in Tajikistan, where relatives or acquaintances might have salient information.

Mr Kurt R. Rice, the department's acting assistant director for threat investigations, told Tajik journalists in September that Khalimov's US training made him a particular danger, but he did not elaborate on Khalimov's role in the terrorist group, also known as ISIL.

"He can use this knowledge to create difficulties for our countries," Mr Rice said. "He's a person who can create difficulties."

Mr Rice's office declined a request to interview him about Khalimov's training, citing his travel schedule.

After the State Department announced the reward, an Iraqi news agency, Alsumaria, reported that Khalimov had been promoted to military commander for the Islamic State, replacing Omar al-Shishani, an ethnic Chechen from Georgia who was killed in the airstrike. Russian news outlets have also said Khalimov was promoted, but neither those accounts nor the Iraqi report could be independently verified.

"The US putting a bounty on his head is significant," Mr Charlie Winter, a senior research fellow at the International Centre for the Study of Radicalisation, in London, said in a telephone interview.

"But it's not possible to know if he's the strategist of military operations."

Further muddying the picture, the SITE Intelligence Group, which monitors extremist propaganda, has found no formal ISIS announcement of Khalimov's position, according to Mr Adam Raisman, an analyst who studies the group's postings.

If Khalimov was, in fact, promoted, he would be the second ISIS commander in chief to have been trained in US military aid programmes in the former Soviet Union. Al-Shishani, whose real name was Tarkhan Batirashvili, had served in the Georgian army, which is equipped and funded by the US as a bulwark against Russian expansion.

US military aid to Tajikistan is more narrowly focused on fighting terrorism and narcotics, because the country is a close ally of Russia. The aid has flowed even though Tajikistan is ruled by an eccentric and authoritarian president, Mr Emomali Rakhmonov, whose police forces are often accused of abuses.

Along with jailing dissidents and using excessive force - in one case, killing 20 civilians in a paramilitary action - Rakhmonov's police forces have been accused of more unusual human rights abuses. A provincial governor recently said that he had forcibly shaved the beards of 13,000 men suspected of sympathising with fundamentalist Islamists.

Muhiddin Kabiri, exiled leader of Tajikistan's main opposition party, the Islamic Renaissance Party, said in a telephone interview that Khalimov "was always against the moderate opposition" and that his police unit was known for abuses, but that the US had turned a blind eye.

The State Department provided five training courses for Khalimov, three of them in the US, including at least one run by the company once known as Blackwater in Baton Rouge, Louisiana.

A spokesman has said the department vetted Khalimov and did not violate the Leahy Law, which prohibits the government from providing military training to foreign military units that violate human rights.

With US training programmes on his resume, Khalimov became commander of a paramilitary police force in 2013, raising alarm among human rights groups about the training even before he defected to the Islamic State.

"The US military has been providing a lot of expertise and training to abusive and repressive governments in Central Asia," Mr Steve Swerdlow, a senior researcher for Human Rights Watch, said in a telephone interview.

"Military cooperation has to be contingent on human rights," he said. "Tajikistan got a free pass despite the atrocious situation with human rights."

US military training programmes are generally carried out by the Defence Department but overseen by the State Department, an arrangement that broke down in Tajikistan, according to a 2015 report by the State Department's Office of the Inspector General that looked into the US response to the Tajik police operation that killed 20 civilians in 2012.

Khalimov, then a deputy commander of the special police unit, took part in that operation but still continued his US military training until 2013.

The report found that the Office of Military Cooperation, the Pentagon group that arranged training for the suspect police units, had also conducted the investigation into the killings - effectively determining that Khalimov's training was legal - rather than the political section of the US Embassy in Tajikistan, which should have overseen the military education programs.

The report concluded that the lack of oversight undermined "confidence that the embassy provides a full and reliable picture of local developments." While it is unclear exactly what training Khalimov received, a 2008 diplomatic cable from the embassy released by the anti-secrecy group WikiLeaks explained what the paramilitary police and other units requested.

The groups wanted training in "mission analysis and the military decision making process, intelligence preparation of the battlefield, direct action, raids and ambushes, special reconnaissance, close quarters combat and battle, sniper and observe operations, military operations in urban terrain".