Four police officers have been killed in a bomb blast set off by rebels fighting Indian rule in a northwestern town in disputed Kashmir, according to police.

The explosion ripped through a market in the town of Sopore on Saturday, police spokesman Harmeet Singh told Al Jazeera.

"A group of four policemen who were on law-and-order duty were killed," Singh said. "Ten shops were also damaged due to the blast, as it was very strong."

Muneeb Ahmad, who lives a kilometre away from the market, told Al Jazeera he "felt the earth shake beneath my feet" when the powerful bomb was detonated.

The attack came as the town was observing a strike to mark the 25th anniversary of a massacre in which government forces killed 57 civilians.

Jaish-e-Mohammad, a Pakistan-based armed group, has claimed responsibility for the blast.

Disputed territory

Fighters from the group were also involved in a marathon gun battle at a paramilitary base on January 1. The fighting at the Lethora-based camp, in southern Kashmir, killed five Indian soldiers and three fighters.

Roughly half a million soldiers are stationed in the disputed territory, which is claimed by both India and Pakistan.

Since 1989, rebel groups have been fighting for the Indian-administered portion to become independent or merge with Pakistan. Nearly 70,000 people have been killed since the uprising began.

The Indian government and its security apparatus have been frequently accused of violating human rights and carrying out extrajudicial killings.

In Kashmir, which has a Muslim majority, most people support the rebels' cause against Indian rule.