A string of arrests of prominent Rwandan military figures, some of them close to the central African nation's inner circle of power, has prompted speculation of a major political crisis.

Analysts and experts say it remains unclear whether Rwandan President Paul Kagame, who has led the country since his rebel army ended the 1994 genocide by Hutu extremists, faces a serious challenge to his leadership or whether the purge is merely designed to keep potential challengers on their toes.

Last month former presidential guard chief and serving colonel, Tom Byabagamba, and retired brigadier-general Frank Rusagara were charged in a Kigali court for inciting rebellion by "spreading rumours". A retired captain, David Kabuye, was also detained.

Critics of Kagame say the arrests expose the workings of a paranoid state that is increasingly nervous over the activities of the dissident Rwanda National Congress (RNC), an exiled opposition group that includes several former top members of the ruling Rwandan Patriotic Front (RPF).

"Any critic is immediately associated with the RNC, even though sometimes there is no connection," said Rene Mugenzi, a Rwandan human rights activist exiled in Britain.

He said the latest arrests targeted people seen as "loose cannons" who were too outspoken, and that the authorities appeared worried that the RNC, which includes several former military brass, had managed to maintain their contacts in the armed forces.

The often bizarre inner workings of Kagame's ruling party regularly lead to officials falling in and out of favour and being promoted or demoted -- and even jailed -- just to keep them on an uncertain footing.

But some analysts said there may be genuine concern about the threat from the dissident RNC.

"I would not rule out that those arrested are suspected of links" with the RNC, said the Belgian academic Filip Reyntjens, a fierce critic of Kagame.

He said the RNC was currently the central preoccupation of the Rwandan government, especially given that a former Rwandan chief of staff and founding member of the RNC, General Faustin Kayumba Nyamwasa, "has kept many contacts in the military, where he was rather popular."

Another co-founder of the RNC, Rwanda's former intelligence chief Patrick Karegeya and once a comrade-in-arms of Kagame, was murdered on New Year's Eve in Johannesburg.

- 'Total obedience' -

The Rwandan government has denied allegations that it assassinated Karegeya, although it does accuse the RNC of links to the FDLR, a Hutu extremist group based in Democratic Republic of Congo that includes former genocidaires.

Authorities have also been tight-lipped over the arrests, with Rwandan army spokesman General Joseph Nzabamwita insisting that it was a criminal matter and that investigations were ongoing.

Rwanda's president, who came to power as leader of an ethnic Tutsi rebel army, has been widely credited with stabilising and transforming the country in the wake of the 1994 genocide during which at least 800,000 people, mostly Tutsis, were killed by Hutu extremists.

The country has clocked strong and steady economic growth, and scores highly on league tables for business friendliness and anti-corruption measures -- thanks in part to the fact that Kagame runs a very tight ship with a single-minded focus on the national interest.

In contrast, the same conduct has earned him increased criticism from rights groups, who say Rwanda is a democracy in name only where all dissent is crushed.

Kagame recently held a party meeting during which he scolded unnamed party officials, telling them that "nobody owes you anything" regardless of any "past sacrifices".

According to a Western specialist on Rwanda, the arrests can be explained in this context -- even though he admitted that it was difficult to have a clear explanation of what was going on inside the Rwandan government.

"There is a serious internal crisis within the central core" of the RPF, but there is also a "system of rotation, demotion, promotion and arrests that is imposed on everyone in the state hierarchy," he explained.

"It aims to keep reminding them that they hold such positions because it is in best interests of the country, the party and the president, and not because of personal skills or services rendered," said the analyst, who did not give his name, adding that the underlying message is that nothing less than "total obedience" is required.

Rwanda has seen similar arrests of top military brass in the past, on charges ranging from corruption to "immoral conduct." But few have been tried, and some have returned to their posts or have even been promoted.