KUALA LUMPUR, Malaysia (AP) - Malaysian police arrested the eldest daughter of jailed opposition leader Anwar Ibrahim for alleged sedition on Monday, a move slammed by critics as a clampdown on dissent. Nurul Izzah Anwar was detained to assist police in their investigation of an opposition rally and also for making "contemptuous remarks that those in the judiciary system had sold their souls to the devil," national police chief Khalid Abu Bakar said in a statement. A lawmaker and a vice president of her father's People's Justice Party, Nurul Izzah was detained because of a speech she made last week in Parliament, said Fahmi Fadzil, the party's communications director. He said the arrest was "ridiculous and outrageous," noting that lawmakers have immunity over comments made in Parliament. Fahmi said the move was intended to silence the opposition after Anwar was jailed for five years last month when he lost a final appeal against a sodomy conviction. Anwar's family said the arrest was "nothing short of intimidation and an abuse of power." Nurul Izzah went to police voluntarily to give a statement about the opposition rally she participated in earlier this month, said her sister Nurul Nuha Anwar. "We maintain that the arrest of our sister is illegal and unconstitutional. We deplore the glaring selective persecution," Nurul Nuha said in a family statement, calling for the release of her sister. Khalid said she will be released once police complete their interrogation. Anwar's arrest was widely seen at home and abroad as politically motivated to eliminate any threats to the ruling coalition, whose popularity has been eroding since 2008 after more than five decades of unquestioned dominance. Anwar and his three-member opposition alliance were seen as the most potent political threat to Prime Minister Najib Razak's ruling coalition. Anwar led his alliance to unprecedented gains in 2008 elections and made further inroads in 2013 polls. Najib's National Front coalition won with a slimmer majority and lost the popular vote to the opposition. The United States voiced deep concern over Nurul Izzah's arrest, and said recent investigations and charges of sedition against critics raise serious concerns about freedom of expression, rule of law and judicial independence. "To further restrict freedom of expression will only lead to further erosion of important pillars of Malaysia's democratic system," State Department spokeswoman Jen Psaki said in Washington. Human Rights Watch called for the government to end its "campaign of abuse" against opposition figures. "Prime Minister Najib needs to recognize that every sedition arrest of an opposition political leader is another step towards the destruction of rights-respecting democracy in Malaysia," Phil Robertson, the group's deputy Asia director, said in a statement.