Gen Rzayev became air force chief after Azerbaijan's independence
The commander of Azerbaijan's air force has been shot dead outside his house in the capital, Baku, officials have said.
Lt-Gen Rail Rzayev, 64, was shot once in the head by an unknown gunman while getting into his car in a western area of the city at around 0800 (0400 GMT).
Defence ministry officials said the general was taken to a military hospital, but died shortly afterwards.
The authorities say they have launched an investigation into the murder, but they do not know what the motive was.
Nijmedin Sadykhov, the head of the Azeri military general staff, told Lider TV that security cameras near Gen Rzayev's home might help catch the perpetrator.
"There was a single shot. According to preliminary information, Rzayev's car had been under surveillance for several days," he said.
Gen Rzayev, who had commanded Azerbaijan's air force since 1992, was rarely seen in public or in the media.
He was the first high-ranking military official to be killed in the former Soviet state since 1994, when the country was at war with Armenia over the disputed territory of Nagorno-Karabakh.
Since then, a fragile ceasefire has held in the region, but there is still no lasting resolution as to how the territory should be governed.
More recently, the general was the Azeri representative in the stalled negotiations between Russia and the US over the use of the Qabala radar station in northern Azerbaijan.
Moscow had offered Washington access to data from the Soviet-built radar station, which it leases from the Azeri government, as an alternative to US plans to station elements of a missile defence shield in Eastern Europe.
Azerbaijan, which lies on the Caspian Sea and has major oil and gas resources, has recently invested much of its wealth into the military.
Official statistics show the government spent more than $1bn (£696m) on improvements to its armed forces last year.
Some military analysts say Gen Razayev played a role in the country's recent large-scale military acquisitions.
"Rzayev was the focal point for air force and air defence military acquisitions, and the largest part of [Azerbaijan's] military budget is being allocated for acquisitions in these spheres," Baku-based analyst Uzeir Jafarov told the AFP news agency.
In October 2008, the International Crisis Group described Azerbaijan's armed forces as "fragmented, divided, accountable-to-no-one-but-the-president, un-transparent, corrupt and internally feuding", and highlighted problems in supply and procurement.
"A lack of transparency and parliamentary oversight of tenders for military construction and food and other purchases for the army allows inflated prices and proxy companies to receive preferential treatment," it said in a report.
However, the BBC's Tom Esslemont in Baku says it is too early to say whether the general's role in such decisions may have formed any part of a motive for his murder.
Foreign diplomats have also warned that the mainly Muslim country, which borders Iran and Russia's troubled Caucasus region, also faces a real threat from Islamic extremism.
Azerbaijan's President, Ilham Aliyev, won re-election in October in a vote which international observers said fell short of fully democratic standards.
He took over power from his father, Heydar Aliyev, who was president for 10 years until his death in 2003.
The country will vote in a referendum in March on the scrapping of a two-term limit on the presidency, which would allow Mr Aliyev to run again for office after his current term ends in 2013.