Pakistani activists poured into the streets on Friday shouting 'Death to America' and burning effigies of President Barack Obama after a US court jailed a woman scientist for 86 years. In a case that has been condemned across the nuclear-armed Muslim nation of 167 million, the government said it would petition Washington to secure the repatriation of the mother of three on humanitarian grounds. A New York court found Aafia Siddiqui, the once brilliant scientist dubbed 'Lady Qaeda' by the US tabloids, guilty of the attempted murder of US military officers in Afghanistan in 2008 -- five years after she disappeared. In Karachi, Siddiqui's home town and Pakistan's largest city, police fired tear gas shells to prevent scores of people from marching on the US consulate at the behest of the youth wing of Islamist party Jamaat-e-Islami (JI). The protestors shouted 'Death to America,' 'Allahu akbar' (God is greater), 'Free Aafia Siddiqui' and 'Down with the US system of justice'. Hundreds of anti-riot police deployed on the main Shahra-e-Faisal road to stop protesters from marching towards the US mission. Police official Javed Akbar Qazi said police arrested at least 14 people for creating a disturbance. At a small protest outside the Karachi press club, JI activists burnt a crudely made Obama effigy, condemning US policies as anti-Muslim. Fowzia Siddiqui, who has vowed to lead a national movement to campaign for her sister's freedom, told a rally of hundreds of heavily veiled women that the Pakistani government had failed miserably. 'The sentence bears testimony to the fact that this government is puppet of the US... We are peaceful people and our aim is to bring back Aafia.' Hundreds more took to the streets in Pakistan's second largest city of Lahore. Cricket hero-turned-politician Imran Khan led a rally to condemn the verdict as 'unethical and inhuman,' an selfnews reporter said. They condemned President Asif Ali Zardari and Khan, who heads the party Pakistan Tehreek-i-Insaf (Pakistan Movement for Justice), warned that the verdict could fan anti-Americanism across Pakistan and the Muslim world. In Islamabad, police stopped dozens of Islamic students from marching on the US embassy to hand over a protest note. The crowd shouted 'Crush America,' 'Siddiqui is our sister' and 'We will bring her back.' Dozens of lawyers and activists blocked traffic in the central city of Multan, shouting 'Down with America' and setting fire to an effigy of Obama and former Pakistani president Pervez Musharraf, an selfnews reporter said. Siddiqui, 38, who as a student excelled at the Massachusetts Institute of Technology, was found guilty of grabbing a rifle at an Afghan police station where she was being interrogated in 2008 and of trying to shoot US servicemen. Prosecutors said she picked up the weapon and opened fire on those servicemen and FBI representatives trying to take her into detention. She missed and in a struggle was herself shot by one of the US soldiers. Defence lawyers argued there was no physical evidence, such as fingerprints or gunpowder traces, to show Siddiqui even grabbed the rifle. Siddiqui's lawyers have said they will appeal against the sentence and her family vowed to launch a 'movement' to get her released from jail. Prime Minister Yousuf Raza Gilani told the upper house of parliament: 'We will use every means to bring her back. Doctor Aafia is the daughter of the nation. We fought for her and we will fight politically to bring her back.' Interior Minister Rehman Malik said the government would petition the US administration to review the sentence on a 'humanitarian basis' and request that Siddiqui be handed over to Pakistan and dealt with under Pakistani law. Asked under what circumstances Siddiqui could return home, the foreign ministry said Obama could pardon her, or an agreement could be reached for her to serve at least part of her sentence in Pakistan. The Human Rights Commission of Pakistan called on Islamabad and Washington to negotiate urgently for her repatriation on humanitarian grounds. 'We fear that the verdict will be misunderstood in Pakistan and bring relations between the two allies in the war on terror under increased strain,' said its chairman Mehdi Hasan. 