Kazakhstan's Emergency Ministry said in a Telegram statement that those on board included five crew.
At least 29 have been hospitalised, the ministry told Russia's state news agency RIA Novosti. More than 30 people were likely dead.
The Embraer 190 aircraft made an emergency landing three kilometres from the city, Azerbaijan Airlines said earlier.
Prosecutor General's Office in Azerbaijan reported that at least 32 people survived the crash, adding that the number wasn't final.
The plane was originally scheduled to travel from the Azerbaijani capital of Baku to the Russian city of Grozny in the North Caucasus.
According to Azerbaijan Airlines, 37 passengers were Azerbaijani citizens. There were also 16 Russian nationals, six Kazakhstani and three Kyrgyzstani citizens.
RIA Novosti quoted Russia's civil aviation authority, Rosaviatsia, as saying that preliminary information showed that the pilot had chosen to divert to Aktau after a bird strike on the aircraft led to "an emergency situation on board".
Mobile phone footage circulating online appeared to show the aircraft making a steep descent before smashing into the ground in a fireball.
Other footage showed part of its fuselage ripped away from the wings and the rest of the aircraft, lying upside in the grass.
The footage corresponded to the plane's colors and its registration number.
The Azerbaijan Airlines plane broke up after crashing near the Kazakhstani city of Aktau. (AP PHOTO)
Some of the videos posted on social media showed survivors dragging fellow passengers away from the wreckage of the plane.
Flight-tracking data from FlightRadar24.com showed the aircraft making what appeared to be a figure-right once nearing the airport in Aktau, its altitude moving up and down substantially over the last minutes of the flight before impacting the ground.
In a statement, Azerbaijan Airlines said it would keep members of the public updated and changed its social media banners to solid black.
Azerbaijan's state news agency, Azertac, said that an official delegation consisting of Azerbaijan's emergency situations minister, the country's deputy general prosecutor, and the vice president of Azerbaijan Airlines had been dispatched to Aktau to conduct an "on-site investigation".
Azerbaijani President Ilham Aliyev, who had been traveling to St Petersburg, returned to Azerbaijan on hearing news of the crash, the president's press service said.
Aliyev was due to attend an informal meeting of leaders of Commonwealth of Independent States, a bloc of former Soviet countries founded after the collapse of the Soviet Union.
Aliyev expressed his condolences to the families of the victims in a statement on social media.
"It is with deep sadness that I express my condolences to the families of the victims and wish a speedy recovery to those injured," he wrote.
Russian President Vladimir Putin spoke to Aliyev on the phone and expressed his condolences, Kremlin spokesman Dmitry Peskov told reporters.
Both Kazakhstani and Azerbaijani authorities were investigating the crash.
Embraer told the Associated Press in a statement that the company was "ready to assist all relevant authorities."
With Reuters
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