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

The Embraer 190 aircraft that was supposed to fly northwest from the Azerbaijani capital Baku to the city of Grozny in Chechnya 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 the 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."

Azerbaijan Airlines reported that 67 people were on board -- 62 passengers and five crew members.

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

"A plane doing the Baku-Grozny route crashed near the city of Aktau. It belongs to Azerbaijan Airlines," the Kazakh transport ministry said on Telegram.

Azerbaijan Airlines, the country's flag carrier, said the plane "made an emergency landing" around three kilometres (1.9 miles) from Aktau.

The Kazakh ministry said its staff put out a fire which broke out when the plane crashed.

It said 150 emergency workers were at the scene.

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

Azerbaijan Airlines initially said the plane flew through a flock of birds before withdrawing the statement.

"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.

It said an investigative team led by the deputy prosecutor general of Azerbaijan has been dispatched to Kazakhstan and is working at the crash site.

Kazakhstan's prosecutor in charge of transportation cases, Timur Suleymanov, said the plane's flight data recorder had been found, Interfax news agency reported.

The health ministry said a special flight was being sent from the Kazakh capital Astana with specialist doctors to treat the injured.

Azerbaijani President Ilham Aliyev declared a day of national mourning today and cancelled a planned visit to Russia for an informal summit of leaders of the Commonwealth of Independent States (CIS), a grouping of former Soviet nations.

Russian President Vladimir Putin held a phone conversation with Aliyev and also "expressed his condolences in connection with the crash", his spokesman Dmitry Peskov told a news conference.

A Russian emergency situations ministry had been sent to Aktau with medical personnel and other equipment, Putin said later as he opened the CIS leaders' meeting in Saint Petersburg.