Pakistani authorities placed opposition leader Nawaz Sharif under house arrest Sunday to stop him from taking part in a major anti-government rally, a spokesman said. The move against former Prime Minister Sharif shows Pakistan's determination to squelch Monday's rally in the capital Islamabad but risks igniting anger among his supporters. It will also likely damage the democratic credentials of the one-year-old government led by US-backed President Asif Ali Zardari. The arrest order came hours after the government announced its first major concession in the monthlong political crisis by pledging to appeal a disputed court ruling against Sharif and his brother. Sharif's spokesman Pervez Rasheed said hundreds of police surrounded his house Sunday in the eastern city of Lahore. He said officers showed Sharif aides a detention order stipulating Sharif and his politician brother Shahbaz Sharif were to be placed under house arrest for three days. Shahbaz was not at home, said Rasheed.