KIGALI (Reuters) - A jailed Rwandan opposition leader was in court on Monday to appeal against her conviction in a case linked to the 1994 genocide after a trial last year that Amnesty International called "flawed".

Victoire Ingabire, head of the unregistered FDU-Inkingi party, was imprisoned for eight years in October for conspiring to harm the country through armed force and terror and for seeking to minimize the genocide in which more than 800,000 people died.

Ingabire returned to Rwanda in January 2010 from exile in the Netherlands to contest a presidential election that year but was barred from standing after being accused of the crimes linked to genocide denial.

President Paul Kagame, who won the 2010 vote in a landslide, has secured international praise for rebuilding Rwanda after the mass killings. But critics accuse him of being authoritarian and trampling on media and political freedoms, charges he rejects.

"We appeal on a number of grounds relating to the unfairness of the trial procedure and misapplication of the law," Iain Edwards, a barrister for Ingabire, told Reuters on Monday, when a Rwandan court started hearing the case.

Several hearings would be held during the period until May 15, when the court was expected to adjourn to consider a verdict, he added.

Ingabire, whose appeal was filed last year, denied charges brought against her.

The prosecution has also appealed against the court ruling last year. It is challenging Ingabire's acquittal on accusations of forming an armed group and other charges and is seeking a longer jail term, Edwards said.

Sarah Jackson, acting deputy director of Amnesty's Africa Programme, said in a statement that Ingabire's "initial trial was flawed and international standards were flouted" and called for a fair appeal to restore confidence in the judicial system.

"Critics of the Rwandan authorities have been harassed, intimidated and imprisoned," said Jackson. "A fair appeal will show that political trials will be dealt with independently."

Martin Ngoga, Rwanda's prosecutor-general, accused Amnesty of making remarks that were "a direct affront to the independence of Rwanda's judiciary". The Supreme Court also issued a statement saying Amnesty should wait before commenting.

Four others were jailed alongside Ingabire but received shorter prison terms. One has already been released and lawyers for two others were in court on Monday to argue their clients should have already been freed.

More than 800,000 people were killed in Rwanda when an ethnic Hutu-led government and ethnic militias went on a 100-day killing spree in April 1994, indiscriminately murdering Tutsis and moderate Hutus.

Amnesty and other rights groups say Kagame made statements in the media and on Twitter about Ingabire's alleged guilt, which they say denied her a right to a presumption of innocence.

Rwanda has long faced calls for political space to be opened up in the country. Frank Habineza, president of the unregistered opposition Democratic Green party, said his party was facing difficulties registering for a parliamentary election this year.

Kagame has dismissed the criticism, and said in February it was up to the opposition to organize themselves.

(Reporting by Jenny Clover; Additional reporting and writing by Edmund Blair in Nairobi; Editing by Andrew Heavens)