Kigali - Rwandan police have arrested Diane Rwigara, a leading critic of Rwandan President Paul Kagame and a women's rights activist, for alleged offenses against state security.Rwigara's mother and sister were also detained on the tax evasion charges and she is also being charged with forgery, Rwanda police said in a Twitter post on Sunday. The three who were arrested on Saturday have been under investigation and police have interrogated them several times."During ongoing investigations, police uncovered credible evidence linking the trio to offenses against state security," Rwanda police said.Police said earlier the three refused to cooperate with police and publicly revealed information that is, by law, supposed to be confidential. Rwigara was a women's rights activist before she announced plans to seek the presidency in last month's election. Rwanda's electoral board disqualified her, saying she didn't have enough signatures to support her candidacy.Her brother, Aristide Rwigara, told The Associated Press that his sister is being persecuted for having dared to challenge Kagame, the longtime president, in Rwanda's August election. He also said the criminal allegations against the family are fabricated, insisting they have been targeted by Rwanda's government for refusing to do business with the ruling party."These charges are absurd. Every day, authorities in Kigali come up with something new against my family," Aristide said, speaking from the United States.Rwigara's troubles started this year after she announced she would challenge Kagame in the August 4 vote. Two days after declaring her candidacy, nude photographs allegedly of her were leaked on social media. It was not clear who was behind the leak.Rwanda has won praise for its advances in economic development and women's rights over the last 20 years, but critics say Kagame rules with an iron fist and tolerates little criticism.