ISLAMABAD: Pakistani opposition figures ramped up calls for the fall of Prime Minister Nawaz Sharif’s government on Saturday, but failed to attract massive crowds of protesters promised at rallies in the capital.

Addressing protesters he had led from the eastern city of Lahore, cricketer-turned-politician Imran Khan said he would stage a sit-in that would continue until Sharif leaves office, lashing out at the government he claims was elected fraudulently. He said enthusiasm can be contained only to a certain limit and warned that his “Tsunami” march can even storm into the Parliament and Prime Minister House.

Meanwhile populist cleric Tahirul Qadri demanded Sharif’s arrest over what he alleged was the murder of his supporters, and called for the installation of an interim national government.

“Nawaz Sharif and Shahbaz Sharif have no right to sit in the government, their cabinets should be dissolved and they should be arrested on murder charges,” Qadri said.

Shahbaz is the younger brother of Sharif and chief minister of largest Punjab province.

Lawyer Mansoor Afridi, who represents Qadri’s Pakistan Awami Tehreek (PAT) movement, said a Lahore court had ordered police to investigate the murder claims, but Information Minister Pervez Rashid denied any order was made to arrest Sharif and his brother.

On June 17, at least 10 PAT workers were killed in clashes with police at Qadri’s headquarters in Lahore and a judicial commission was formed to probe the killings.

The May 2013 general election saw Sharif take power in a landslide, and international observers who monitored the polls said they were free and credible.

The demonstration is the culmination of the “long march” — in reality a motorized cavalcade — that set off Thursday from Lahore, situated around 300 kilometers away, to try to topple the government.

Police and witnesses said on Friday that activists from Khan’s Pakistan Tehreek-e-Insaaf (PTI) party clashed with supporters of Sharif’s Pakistan Muslim League-N (PML-N) in the town of Gujranwala, some 200 kilometers southeast of Islamabad.

The marchers took more than 36 hours to reach the capital as convoys made stopovers in various cities along the road, where they were warmly welcomed by supporters.

Supporters of PTI, which came third in last year’s election, lined up to welcome the convoy in towns along the Grand Trunk Road that links Lahore and Islamabad.

Both Khan and Qadri had originally planned for their marches to converge on Islamabad on Thursday, Pakistan’s independence day, but they made slow progress.

By Friday evening Khan’s march was slowed to a snail’s pace by PTI well-wishers.

Security in Islamabad has been ramped up in recent days, with more than 20,000 police and security forces on the streets.

The government has agreed to allow the two groups to hold rallies but many of the city’s streets are blocked off with shipping containers to protect sensitive areas.

Government officials have accused march organizers of trying to derail democracy and Sharif said the marches were a distraction from more pressing issues.

Pakistan is waging a military offensive against Taleban hideouts in the northwest, while also trying to boost a sagging economy and solve a chronic power supply crisis.

Prime Minister Sharif who took office just a year ago in the first democratic transfer of power in a country long plagued by military coups, has said he’ll stay in power, raising fears of possible political instability in this nuclear power.

Rana Sanaullah, a senior leader of Sharif’s ruling party, said the government was ready to investigate allegations of electoral fraud, but ruled out Sharif could be removed through a rally. Sharif won a landslide election in May 2013.

Imran Khan late Friday said a police officer gave him a letter from the provincial Punjab government, warning that the Punjabi Taleban had planned to kill him.