Anti-government protesters have clashed with police in the Pakistani city of Lahore as fears grow about the country’s stability.Violence erupted after opposition leader Nawaz Sharif was placed under house arrest. Government officials admitted sealing off Sharif’s house but said it was for his own protection. Sharif defied restrictions on his movements and he called on supporters to take to the street. Pakistan’s president Asif Ali Zardari, the leader of the ruling PPP party, has refused to bow under pressure to diffuse a political deadlock that has paralysed the country. The US and UK, increasingly alarmed at the situation in a country pivotal to efforts to contain international terrorism, have urged the two sides in Pakistan to find a way forward. For much of the PPP’s one year in power Pakistan has been stymied by a power-struggle between the government and the Pakistan Muslim League of Mr Sharif. Police have detained hundreds of lawyers and opposition activists in a crackdown launched to prevent their so called “long march” protest that is due to climax with a sit-in outside parliament in Islamabad on Monday. The lawyers want the former chief justice re-instated. The Pakistan Government has refused Some elements of the Pakistan Army are said to be alarmed as Pakistan’s security situation deteriorates but observers say a military coup is thought to be unlikely.