Security restrictions and a strike has shut down most of Indian-administered Kashmir, after clashes between militants and government forces killed at least 20 people.

Shops and businesses were closed in most parts of the restive region on April 2 after separatist leaders fighting against Indian rule called for a shutdown to protest the killings.

Curfew-like restrictions were in place in the main city of Srinagar and other towns where additional troops were deployed and barricades installed to prevent protests.

Schools and colleges were also shut in light of the tensions, while mobile Internet services were suspended to make it harder to organize protests.

Four civilians were reported killed when police opened fire on stone-throwing demonstrators rallying against anti-militancy operations in southern Kashmir on April 1. Three Indian soldiers and 13 militants were said to have died in gunbattles.

Officials said it was the disputed region's worst loss of life during a single day in recent years.

Neighboring Pakistan condemned the violence as a "mindless killing spree" and said those slain were innocents.

"Such cowardly actions of the occupying forces only serve to fortify the resolve of the Kashmiri people," the Foreign Ministry said.

Kashmir has been divided between Hindu-majority India and Muslim Pakistan since the end of British rule in 1947. Both claim the region in its entirety and have fought two wars over it.

A secessionist movement turned violent in the late 1980s, with many fighters crossing the border from Pakistan into India, leading New Delhi to increase its military presence in the region.

New Delhi frequently accuses Islamabad of arming, training, and sending fighters across the Line of Control to launch attacks on its soldiers in Kashmir.

Pakistan denies the allegations, saying it only provides diplomatic support to the Kashmiri struggle for the right to self-determination.

The region has been hit by an upsurge in violence in 2018, with at least 51 suspected militants killed since the start of the year.

With reporting by AFP, Reuters, AP, Times of India, Pakistani Observer, and The New York Times