The head of Azerbaijan's air force has been shot dead outside his home in the capital Baku, an interior ministry spokesman has said.

Lieutenant General Rail Rzayev, who died in a hospital after being shot in the head, is the most senior official to have been killed in Azerbaijan since the country's war with neighbouring Armenia in 1990.

Sadiq Gozalov, the interior ministry spokesman, said military prosecutors would be probing Rzayev's killing on Wednesday.

He said he had no information regarding a possible motive for the shooting.

Oil rich Azerbaijan is part of the strategically important but fragile South Caucasus where Russia and the US are still competing for influence.

The ex-Soviet republic hosts a pipeline pumping Caspian Sea oil to world markets.

Azerbaijan is locked in a dispute with Armenia over the Nagorno-Karabakh region where ethnic Armenian separatists threw off Azeri rule in a 1990s war that killed about 35,000 people.

The two countries are technically still at war.

Rzayev headed Azerbaijan's air force since 1992.