BAKU (Reuters) -- The air force chief of Azerbaijan, a key oil producing state in the volatile southern Caucasus region, has been shot dead outside his home.
Lieutenant General Rail Rzayev was the most senior official to have been killed since assassinations in the 1990s that were blamed by authorities then on organized crime or attempts to undermine government.
Police and defense officials in Azerbaijan, a mainly Muslim country where Russia and the United States vie for influence, said it was not immediately clear what the motives for Rzayev's killing were.
"At approximately 8 a.m. (0400 GMT) at the entrance to his home the head of the air force and missile-defense system was shot in the head and later died of his wounds in hospital," a source in the Interior Ministry said.
Outside Rzayev's home in an upmarket area to the west of Baku's center, four policemen stood guard in the rain.
Nijmedin Sadykhov, head of the Azerbaijani military general staff, told Azerbaijan's private Lider television that security cameras in the vicinity might help in the investigation. He said he had no information on what the motive for the killing could have been.
"There was a single shot. According to preliminary information, Rzayev's car had been under surveillance for several days," he said.
Officials said his funeral will be later on February 11, in accordance with Muslim tradition.
Azerbaijan saw a series of high-level murders in the 1990s, with victims including the deputy speaker of parliament. In the past few years, a small number of prosecutors and police officials have also bee murdered.
The authorities blamed those killings either on organized crime or attempts to destabilize the country.
In the past decade, Azerbaijan has arrested dozens of people suspected of belonging to militant Islamist groups, and in 2007 it said it foiled a plot by Islamists to stage an armed attack on the U.S. Embassy in Baku.
Refueling Stop For U.S.
Ex-Soviet Azerbaijan lies on the Caspian Sea coast and is the entrance point to a pipeline, operated by a BP-led consortium, pumping oil from Central Asia to Europe.
It has been run since 2003 by President Ilham Aliyev, accused by some in the West of concentrating too much power in his hands.
The country will vote in a referendum in March on the scrapping of a two-term limit on the presidency, that could allow Aliyev to run for office after his term ends in 2013.
Azerbaijan has close ties to the United States.
U.S. Air Force jets en route to Afghanistan refuel at Azerbaijan's main airport and a 90-strong Azerbaijani military contingent has been serving in Afghanistan with NATO-led forces.
Azerbaijani troops were also serving alongside U.S. forces in Iraq until they withdrew at the end of last year.
Azerbaijan is still technically at war with its neighbor Armenia over the mountainous region of Nagorno-Karabakh, where ethnic-Armenian separatists threw off Azeri control during fighting in the early 1990s.
Rzayez was the Azerbaijani representative in stalled negotiations between Russia and the United States on use of the Qabala radar station in northern Azerbaijan.
Russia had offered Washington access to data from the Soviet-built radar station, which it leases from Azerbaijan, as an alternative to U.S. plans to station elements of its missile-defense shield in Eastern Europe.