An Azerbaijan Airlines passenger jet crashed on Wednesday in western Kazakhstan, killing 38 of the 67 people on board, officials said.

The Embraer 190 aircraft was supposed to fly northwest from the Azerbaijani capital Baku to the city of Grozny in southern Russia, but instead flew across the Caspian Sea and went down near the city of Aktau in Kazakhstan.

The plane's course on Flight Radar website showed it flying away from its normal route and then circling over the area where it eventually crashed near Aktau, which is an oil and gas hub on the eastern shore of the Caspian Sea.

"The situation is not very good, 38 dead," Russia's Interfax news agency quoted Kazakh Deputy Prime Minister Kanat Bozumbayev as saying.

The Kazakh emergency situations ministry reported that "29 survivors including three children have been hospitalised."

The Kazakh transport ministry said the plane was carrying 37 nationals from Azerbaijan, six from Kazakhstan, three from Kyrgyzstan and 16 from Russia.

Azerbaijan Airlines, the country's flag carrier, said the plane "made an emergency landing" around three kilometres from Aktau.

Kazakhstan said it had opened an investigation into the cause of the crash, which was not immediately clear.

"We cannot disclose any investigation results at this time," the office of Azerbaijan's prosecutor general said in a statement.

"All possible scenarios are being examined, and the necessary expert analyses are underway," it added. (AFP)