ISLAMABAD: Pakistani opposition leader Imran Khan vowed Sunday to protest “until the last breath” as ongoing clashes between his supporters and police outside the prime minister’s residence left three dead and hundreds injured.

The violence began Saturday night after thousands of supporters of Khan and firebrand cleric Tahirul Qadri tried to storm Prime Minister Nawaz Sharif’s house using cranes to remove barricades.

By Sunday afternoon clashes were continuing between police in riot gear and a few hundred protesters. Many protesters had come armed with batons and slingshots.

Shipping containers were set ablaze, several vehicles stood torched, and hundreds of tear gas canisters lay strewn on the ground on Islamabad’s normally pristine Constitution Avenue following more than 15 hours of battle.

The opposition groups marched to the capital on Aug. 15 demanding the resignation of Sharif, triggering a crisis that has raised the specter of military intervention.

They claim the 2013 election which swept Sharif to power was rigged, though local and foreign observers rated the polls as relatively fair credible.

Speaking from on top a container, Khan said: “Now I ask all Pakistanis: Rise up against this government. This is not a constitutional government, they are killers.

“We will continue until our last breath. I urge all Pakistanis to come out,” adding he would file murder charges against Sharif for the violence.

Earlier, Information Minister Pervaiz Rashid had said the government remained open to restarting negotiations.

Backed by Parliament and many political parties, Sharif has refused to step down as negotiators have tried to convince Qadri and Khan to end their protests.

Late Saturday night, protesters headed toward the prime minister’s residence. When the crowd started removing shipping containers used as barricades, police fired salvos of tear gas that forced the crowds back. Authorities have said they had no choice but to use force.

Nearly 400 people — including women, children and police officers — were admitted to local hospitals, officials said. The injured had wounds from tear gas shells, batons and rubber bullets, said Dr. Javed Akram, who heads the capital’s main hospital.

“The biggest question: Can Nawaz Sharif survive? The answer, in these frantic hours, must surely be a miserable, despondent no,” read an editorial in Dawn, one of the country’s leading English-language newspapers.

The demonstrations signify the starkest threat to Sharif’s third term as prime minister. His previous term ended with a military coup and his eventual exile. This turn in office has seen equally contentious relations with the country’s powerful army. He’s clashed with the military over the prosecution of the former army chief for treason, accusations the country’s powerful spy agency was behind the attempted killing of a top TV anchor, and a military operation in the tribal areas.

Sharif vowed Saturday he would not step down, but if the violence continues it could severely undermine his authority.