LAHORE, Pakistan (AP) — Violent clashes erupted between Pakistan's security forces and Islamists in the eastern city of Lahore on Friday, killing at least two policemen and injuring several demonstrators, a police spokesman and witnesses said.

The incident happened after thousands of Islamists launched their “long march" from the city toward the capital, Islamabad, demanding that the government release the leader of their outlawed party.

The rallygoers want to go to Islamabad to pressure the government to release Saad Rizvi, the head of the Tehreek-e-Labiak Pakistan party. Rizvi was arrested last year amid demonstrations against France over publishing caricatures of Islam’s Prophet Muhammad.

Pakistan has deployed police and paramilitary personnel to prevent the demonstrators from leaving Lahore. Authorities also suspended cellular service in parts of Lahore and blocked roads.

The situation worsened when police tried to stop the rallygoers, witnesses said.

Rizvi's party said they were peaceful and that police suddenly started firing tear gas shells.

Police spokesman Rana Arif said two of the police officers were killed and another was injured when protesters threw stones. Rizvi's supporters said several protesters were wounded when police swung batons and fired tear gas.

Shipping containers were also being brought in to block the main Islamabad highway and surrounding roads to keep protesters from entering the capital from other nearby cities, towns and villages. Lahore is located about 350 kilometers (210 miles) from Islamabad, and most of the rallygoers are walking, although they had arranged buses and cars to reach the capital in a convoy.

The TLP has a history of staging protests and sit-ins to press their demands.

On Friday, Rizvi's party leader Ajmal Qadri said his supporters launched the “long march" after talks with the government failed to secure Rizvi's release.

Rizvi’s party gained prominence in Pakistan’s 2018 elections, campaigning on a single issue: defending the country's blasphemy law, which calls for the death penalty for anyone who insults Islam. It also has a history of staging violent protests to pressure the government to accept its demands.

The latest development comes at a time when Prime Minister Imran Khan was visiting Lahore.

Khan is expected to leave for Saudi Arabia on an official visit on Saturday.

Friday's rally against Khan's government also comes amid increasing price hike in the country. Surging prices of food, gas, electricity and other items have made him unpopular, although he still holds the majority in the parliament.

Ahmed reported from Islamabad