The twin-engine Antonov An-72 transport jet disappeared from radar screens at about 1900 local time (1300 GMT) as it was circling in a raging blizzard, trying to land at the city of Shymkent, the capital of the South Kazakhstan Region.

It crashed into an open-cast mine, littering the area with mangled, burning fragments.

The plane belonged to the border troops of Kazakhstan's KNB security service. Those killed included the commander of the country's border guards, Turganbek Stambekov, and his wife.

President Nursultan Nazarbayev ordered a national day of mourning on Thursday, his press service said.

"Most probably, the black box (flight recorder) will give us a clue about what caused this catastrophe," KNB chief Nurtai Abykayev told a news conference in Shymkent, according to local media.

"Special commissions that are investigating will look into various possible causes. These can include weather conditions, the human factor or the plane's technical condition. Anything."

The Soviet-designed plane, which can take off from rough gravel runways just 800 metres long, is widely considered to be a reliable and sturdy workhorse of the air forces of several former Soviet states.

The one that crashed near Shymkent was made in 1990, and in November it underwent maintenance at the factory in Ukraine that built it, after which it had accumulated just 40 hours of flight time, including 30 take-offs and landings, local media said.

The plane was carrying officers from Kazakhstan's southern border protection district who had attended an annual meeting in the capital Astana.

Oil-producer Kazakhstan, Central Asia's largest economy, has seen accidents with smaller military aircraft and helicopters during the 21 years of its independence after the collapse of the Soviet Union.

GRIEF AND ANGER

Kazakhstan is predominantly Muslim and according to Islamic tradition the first funerals of those killed in the crash should have been held on Wednesday. But this was not possible because medical experts still had to identify badly mutilated bodies, Abykayev said.

Several distraught relatives could be seen near the cordoned-off crash site on Wednesday. They did not try to conceal their anger and frustration.

"They should have allowed us to take away the remains and bury them," a middle-aged woman, whose brother was among the killed officers, told Kazakhstan's Channel 7 television.

"My brother left four children. They must know where their father died so they can bring flowers here," she said. "He had great plans which will never be realised. He aspired to rise to the rank of general."

Thursday will be the second time Kazakhstan, a vast nation of 17 million people, will observe a day of national mourning this year. In June, the country mourned 14 border guards and a herder killed by a fellow serviceman at a remote border post near China's border.

In one of the world's worst civilian air disasters, an Ilyushin IL-76 cargo plane from Shymkent collided in midair with a Saudia Boeing 747 near New Delhi in November 1996, killing all 349 aboard both planes. (Reporting by Dmitry Solovyov; Editing by Pravin Char)

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