An American aid worker shot dead in central Baghdad has been identified as Stephen Edward Troell, the US embassy based in Baghdad said.

Mr Troell, 45, from Tennessee, was killed by unknown attackers as his car pulled up to the street where he lived with his family in the city’s central Karrada district.

It was a rare killing of a foreigner in Iraq, where security conditions have improved in recent years, even opening the door for tourism.

The embassy said it is closely monitoring an investigation begun by Iraqi authorities but declined to comment further out of respect for Mr Troell’s family, the embassy statement said.

Prime Minister Mohammed Shia al-Sudani ordered a probe in the hours after Mr Troell was killed.

Mr Troell’s body had already arrived at Baghdad’s Sheikh Zayed hospital.

The circumstances surrounding his death and his activities in Iraq are shrouded in mystery.

No group has claimed responsibility for the killing.

Security officials dismissed the possibility it was a kidnapping gone wrong.

As Mr Troell drove towards his home, a car cut him off and assailants in another vehicle opened fire, security officials said.

His wife was in the car with him but unhurt, they added.

Her whereabouts and that of the couple’s children were unknown.

Mr Troell worked for a language centre in Baghdad’s Harthiya neighbourhood and was also reportedly employed by an American non-governmental organisation, Millenium Relief and Development Services.

The Associated Press (AP) spoke to the organisation’s main country office in the northern province of Dohuk, but local authorities said it had not been operating for two years.

Officials also told the AP the NGO was known to conduct Christian missionary work along with its development activities. The officials spoke on the condition of anonymity because they were not authorised to brief media.

The language school, Global English Institute, issued a statement on its Facebook page bidding farewell to Mr Troell. It promised to spread his message of “teaching the English language to spread love and peace for the sake of rebuilding our country”.

Mr Troell’s social media profile shows he was a deeply religious and devoted family man, often posting photos with his wife and three young daughters, with a special devotion for the Middle East. In his Twitter biography, he described himself as living and serving in the region.

In one post, Mr Troell posed with his wife on a Baghdad bridge as the sun set behind them. “What a wonderful place!” he wrote.

In the early years that followed the US-led invasion of Iraq in 2003, such attacks were common.

In 2004, two Americans were kidnapped in Baghdad and extremists later released videos showing their beheading.