ISLAMABAD, Pakistan — A political standoff on the streets of Pakistan’s capital escalated into a national crisis on Sunday after clashes between the police and protesters attempting to storm the prime minister’s house left three people dead and at least 500 wounded, raising the specter of a government collapse.

The violence, in which the police fired rubber bullets and tear gas at protesters armed with sticks, provoked an intervention from the military, which has a long history of seizing power during times of chaos. On Sunday evening, the army chief held an emergency meeting with the military high command, moving it up by a day as the situation in the capital, Islamabad, deteriorated rapidly.

In a statement afterward, the military stressed its commitment to democracy and urged rival politicians to resolve their differences “without wasting any time.” But it also stated that “further use of force will only aggravate the problem,” an assertion that put further pressure on Prime Minister Nawaz Sharif by limiting his options to halt the chaos.

Thousands of protesters, led by the opposition politician Imran Khan and the cleric Muhammad Tahir-ul Qadri, have been camped out on the streets of Islamabad for more than two weeks in a bid to force Mr. Sharif to resign.