By Ian MacWilliam
BBC News, Almaty
The authorities in Kazakhstan have accused a senior parliamentary official of ordering the murder of one of the country's leading opposition figures.
Sarsenbaiuly is the second opposition leader to die recently
Interior Minister Baurzhan Mukhamedzhanov said the official had confessed to ordering the killing of Altynbek Sarsenbaiuly two weeks ago.
But the opposition says it doubts the accused man was the mastermind.
There is suspicion that he is being used as a scapegoat to cover up for the real instigators.
The murder, the second of an opposition figure in three months, has shocked Kazakhstan.
It may yet have wider political repercussions in this usually peaceful central Asian republic.
Mr Mukhamedzhanov said the senate official arrested last week had confessed to ordering the killing of Mr Sarsenbaiuly out of personal enmity.
The bodies of Mr Sarsenbaiuly, his bodyguard and driver were found in hills near Kazakhstan's largest city, Almaty, in mid-February.
Five members of an elite special forces unit have been arrested for allegedly carrying out the killing.
The interior minister gave details of the official's alleged confession despite the fact that the investigation is still continuing and no date has even been set for a trial.
Opposition leaders have called for a broader investigation, including the questioning of President Nazarbayev's son-in-law and his daughter, who was involved in a legal dispute with Mr Sarsenbaiuly.
On Sunday an angry crowd of at least 1,500 protestors marched through Almaty, scuffling with police and denouncing the president because of the murder.
Political killings are rare in Kazakhstan, but this is the second mysterious killing of an opposition figure in the past four months.
Both men were former government insiders who had accused the presidential family of massive corruption. Kazakhstan is set to emerge as a major oil exporter in the coming years.
The furore over these mysterious deaths will be trouble for a government which has been keen to present itself as a politically stable business partner in a troubled region.