Six people were killed and more than two dozen injured on Sunday when police clashed with protesters during a by-election in Srinagar in India-held Kashmir region, a senior police official said.

Suspected separatist factions in Kashmir had called for a boycott of the vote, resulting in heightened security and low voter turnout when the polling began.

Protesters throw stones on Indian security men outside a polling station. ─AP

In Budgam district, police initially used tear gas against protesters who were throwing stones, but then opened fire, killing six people, the senior police official told Reuters.

More than two dozen people were injured during the clashes across central Kashmir on Sunday, the official said.

At least 70 polling stations were shut due to the violence, while at some stations voting machines were set ablaze by the protesters.

The by-election in Srinagar is being held to fill a vacant seat in the Lok Sabha, India's lower house of parliament. A second by-election in the state for a separate Lok Sabha seat is set to take place on April 12 in Anantnag. The results of both polls are expected to be announced on April 15.

Indian forces clash with Kashmiri protestors near a polling station in Srinagar. ─AFP

India-held Kashmir has been in a phase of unrest since last year when Indian security forces killed Hizbul Mujahideen commander Burhan Wani.

The violence since then, largely in the form of troops firing on civilian crowds with shotguns after protesters throw stones, has left 84 civilians dead and more than 12,000 civilians and security force personnel wounded.

Pakistan condemns killings

The Adviser to the Prime Minister on Foreign Affairs, Mr. Sartaj Aziz strongly condemned the brutal killings by Indian occupation forces today when they opened fire on demonstrators during today's events, a press release from the foreign office said.

The press release also called upon the international community to urge India to put an immediate end to the ongoing bloodshedin Kashmir and honor its commitments to hold a transparent, free and fair plebiscite under the auspices of the United Nations.