ISLAMABAD (AFP) - Anti-government protesters in Pakistan have pressed fresh murder charges against Prime Minister Nawaz Sharif, the police confirmed on Wednesday, as demonstrations that rocked the capital last month appear to lose steam.

The case relates to the deaths of three people in clashes with police that took place on the night of Aug 30 after the protesters attempted to storm the prime minister's official residence and used cranes to remove barricades. Two victims died from rubber bullet injuries while a third had a heart attack. All were male.

A senior police official told AFP: "Yes, a case for murder, attempted murder, attack and abetment for attack has been registered against Prime Minister Nawaz Sharif."

He added the that Interior Minister and several senior police were also named. The charge sheet, filed late on Tuesday, was ordered by a lower court last week following a petition by supporters of Dr Tahir ul Qadri, a populist cleric who has led the protests along with opposition leader Imran Khan.

Both leaders allege massive systematic rigging in the 2013 poll that swept Mr Sharif to office, the country's first peaceful transition of power from one civilian government to another in a country long dominated by the military.

Critics of the protesters have said they are being supported by elements of the country's security establishment, a theory that gained some traction after a senior member of Mr Khan's party announced that his party had been taking directions from the army.

A few thousand protesters remain camped outside the country's parliament, their numbers swelling in the evening when Mr Khan and Dr Qadri address them on top of shipping containers.

The authorities have arrested dozens of demonstrators, some of whom were accused of storming a TV station, but most have been subsequently let go due to lack of evidence.

Mr Sharif and other high-ranking figures were also named in a murder case related to the deaths of 14 Qadri supporters in the eastern city of Lahore in June.

The lodging of criminal cases in Pakistan is often used as a tactic to exert pressure on the parties named in order to reach a deal.

By law the police are compelled to investigate the matter but can subsequently drop the case if it lacks merit.

Speaking from the northern city of Attock Wednesday, Mr Sharif said he would not be moved.

"The nation of 180 million people have elected me as a prime minister and how can I resign on the demands of 5000 people?

"Today, the whole nation stands together except a few thousand people."