Nawaz Sharif, the Pakistani opposition leader, has accused the government of running an "elected dictatorship" that is plotting to kill him. As a countrywide crackdown was launched against political activists, Mr. Sharif, a former Prime Minister, told the Guardian in an interview that Asif Zardari, the President, was ruling under a cloak of democracy but his policies would only benefit extremist elements. Pakistan is struggling with an onslaught by homegrown Islamist militants that has left hundreds dead, and the government is fighting to shore up a collapsing economy. But these battles appear to have been sidelined by a confrontation between the two big political parties, Mr. Sharif's Muslim League-N and Mr. Zardari's Pakistan People's party. Mr. Sharif was speaking as the government arrested hundreds of political activists, lawyers and human rights campaigners before a planned mass opposition rally this week. Public gatherings of more than four people were banned in Punjab and Sindh, two of Pakistan's four provinces. Police raided the house of Imran Khan, the leader of the Tehreek-e-Insaaf party and former Pakistan cricket captain. "I have recently received certain information from own sources, credible sources, about certain forces who are active against me," Mr. Sharif said on Wednesday as he was being driven in an armour-plated Mercedes to a political rally. "Threats to my life come from high-ranking government officials, certain topmost people in the government, my sources say." He declined to give further details. It is understood his party has yet to decide how to respond. "The risks are there. I can't abandon my mission because of the risks. It's a very noble cause. A mission to put the country back on the road to democracy," he said. Last month Mr. Zardari dismissed the Muslim League-N government in Punjab province. Elections a year ago, after eight years of military rule under Pervez Musharraf, brought to power an elected government. But Mr. Zardari has failed to reinstate Iftikhar Chaudhry, the chief justice who was removed in 2007 by Gen. Musharraf. Mr. Zardari's aides say Justice Chaudhry is too politicised and Mr. Sharif is using the issue. "Sometimes we [Pakistanis] are caught up in military dictatorships. Now we are caught up in a democratic dictatorship," said Mr. Sharif. "In the garb of democracy we are, frankly, under dictatorial rule." Mr. Sharif's party was briefly in coalition with Mr. Zardari last year before Mr. Sharif stormed out over the issue of the judiciary. But it was Mr. Zardari's move against the Punjab administration that pushed Mr. Sharif from critic to enemy. The province is now run by Mr. Zardari under emergency rule. "Our mandate [in Punjab] has been trampled. He [Mr. Zardari] doesn't show respect to other parties' mandate. It is the worst form of dictatorship," said Mr. Sharif. "He doesn't allow the judiciary to become independent because of his own vested interest. This is what dictatorship is all about." Western governments, led by the U.K. and U.S., have tried to broker a truce between Mr. Zardari and Mr. Sharif. There are fears that if serious civil unrest follows, the Army could step in. There were further diplomatic moves on Wednesday with Robert Brinkley, the British High Commissioner, meeting Yousaf Raza Gilani, the Prime Minister, while Anne Patterson, the U.S. Ambassador, met Rehman Malik, Mr. Gilani's adviser on home affairs. "Only a democratic Pakistan can get rid of extremism. Therefore we've got to put more and more emphasis on strengthening democracy, because that's the only answer," said Mr. Sharif. "Rather than fighting extremism, we [political leaders] are fighting each other." Farhatullah Babar, Mr. Zardari's spokesman, dismissed Mr. Sharif's allegations of a plot to kill him as "political mileage". "This is outlandish," said Mr. Babar. "The government is providing him [Mr. Sharif] protection so that the militants don't take advantage of the situation." A "long march" has been launched by a coalition of parties, led by Mr. Sharif's party, and pro-judiciary groups. The campaign wants the government to appoint independent judges, starting by restoring Justice Chaudhry. The issue of judicial independence has turned into the most incendiary political issue in Pakistan. Setting out from all corners of Pakistan, the protesters aim to converge on Islamabad on March 16. But the government has moved to cut it off. Many activists have gone into hiding for now, promising, though, that the march would proceed, a situation that could lead in the next few days to clashes between demonstrators and the authorities. Paramilitary troops were put on standby. Mr. Sharif pressed on with a political rally in the town of Abbottabad. In Punjab, about 300 political activists were arrested under a colonial-era law that allows for six months' imprisonment. Sherry Rehman, the information minister, accused Mr. Sharif of provoking the clampdown by calling for civil disobedience and refusing to negotiate with Islamabad. "Had the PML-N and the rightwing rump of the former lawyers' movement decided to hold a peaceful rally, the government would have facilitated it, as it has done in the past," Ms. Rehman said. "But Pakistan's constitutional and democratically elected government cannot allow the rule of law to be replaced by the law of the jungle." In a reminder of the extremist menace, Bashir Bilour, a minister in the North-West Frontier Province government, escaped an assassination attempt on Wednesday when a gunman opened fire, wounding two passersby. The attacker later blew himself up, killing at least three other people.