|Victoire Ingabire, the leader of United Democratic Forces, has been arrested by Rwandan authorities [AFP]
Human rights groups have called on Rwandan authorities to allow political opponents "to carry out their legitimate activities" after the arrest of an opposition leader.
Victoire Ingabire, the leader of the unregistered United Democratic Forces (FDU), was arrested on Thursday in Kigali on the basis of information given by a former military officer.
Ingabire, who had already been under judicial control since April, has been detained in connection with an alleged plot to form a "terrorist group", according statements from the police, Carina Tertsakian, a researcher with Human Rights Watch (HRW), told Al Jazeera on Saturday.
"We are asking that the Rwandan government fully respect the rights of opposition party members and allow them to carry out their legitimate activities without fear for their safety," Tertsakian said.
"If Ingabire is to be charged, it should be on the basis of solid evidence, not as a punishment for her criticisms of the government," she said.
According to police, the former military officer who informed on Ingabire was arrested on Wednesday on the border of Rwanda and the Democratic Republic of Congo. Major Vital Uwumuremyi told police he had received the opposition leader's help to "set up a military wing of the FDU," a police statement said.
The charges against them "include buying and distributing arms and ammunitions to the terrorist organisation and threatening national security and public order".
Ingabire was first arrested in April on accusations of associating with a terrorist group, denying genocide that left more than 800,000 people dead in the 1990s, promoting genocide ideology and division.
"She has not been allowed to leave the capital since she was arrested the first time," Tertsakian said.
Rwanda's government was forced to defend itself against allegations of attempting to silence opposition in the run-up to presidential elections in August.
It dismissed accusations that it was behind the murder of the vice-president of the opposition Green Party, the attempted assassination of a former army general and the killing of a journalist who claimed he had evidence of Kigali's role in the attempted assassination.
Authorities also prevented Ingabire from registering the FDU so she could run in the polls, which Paul Kagame, the incumbent president, won with a landslide.
Kagame has ruled Rwanda since his Rwandan Patriotic Front (RPF) ended the 1994 genocide, which largely saw members of the Hutu majority massacre his Tutsi minority.
The government has been lauded by the international community for progress in women's rights and economic growth, but analysts say Kagame's government does not tolerate dissent.
HRW also on Saturday voiced concern about another opposition leader, Bernard Ntaganda, the president of the PS-Imberakuri, who has been in detention since June.
"Ingabire is not the only opposition leader we are worried about - Ntaganda was arrested in June and was rushed to the hospital and we are worried about him," Tertsakian said.
Ntaganda is apparently gravely ill after going on a hunger strike to protest his treatment in prison, and was rushed from Kigali's central prison to the city's main hospital on Friday.
"His relatives and friends reported that he was in intensive care, but were not given specific information on his condition. Some of them were able to see him briefly in hospital and reported that he was very weak," HRW said.