ALMATY (REUTERS) - Kazakhstan jailed six men on Wednesday for conspiring to assassinate government officials, the Supreme Court said, indicating a possible rise of Islamist violence in the oil-rich country.

Kazakhstan, a mainly Muslim nation the size of Western Europe but with a population of just 17 million, had until recently seemed less prone to the religious violence more common in some of the poorer post-Soviet Central Asian states.

The court said the men were part of a "terrorist group"which planned to kill senior officials at the opening of a new opera and ballet theatre in the capital Astana.

One had trained his under-age Muslim wife as a suicide bomber to detonate the charge, it said.

The group was arrested in January.

"Serik Koshalakov, the leader of the criminal group, was sentenced to 10 years in a high-security prison and his property will be confiscated," Supreme Court spokesman Yevgeny Drobyazko said. The other members were sentenced to between five-and-a-half and 10 years.

President Nursultan Nazarbayev, a 73-year-old former steelworker, has ruled the country with a firm hand for more than two decades, overseeing fast economic growth and more than US$170 billion (S$216 billion) in foreign direct investment.

But in recent years the secular nation has been hit by explosions and skirmishes between security forces and radical Islamists.