Two officials at the Pakistan High Commission in New Delhi were being expelled for "indulging in espionage activities", India's foreign ministry said late Sunday, allegations that its nuclear-armed rival called "baseless".

Tensions are already heightened between the neighbouring foes over the Himalayan region of Kashmir, which was split between them in 1947 when they gained independence from Britain.

"The government has declared both these officials persona non grata for indulging in activities incompatible with their status as members of a diplomatic mission," the ministry said in a statement.

The pair had to leave the country "within 24 hours" and Pakistan's charge d'affaires was issued with a "strong protest" over their alleged activities, the ministry said.

Pakistan's foreign ministry said it "strongly rejects the baseless Indian allegations" and called it a "clear violation of the Vienna Convention... especially in an already vitiated atmosphere".

Kashmir has become a bigger source of tension in the relations between the regional powers after New Delhi last year scrapped the restive Muslim-majority region's semi-autonomous status and imposed a curfew to quell unrest.

India and Pakistan have fought three wars against each other since independence, including two over Kashmir.

There has also been numerous flare-ups between the two foes, including in February 2019 when they conducted tit-for-tat air strikes.

Freedom fighter groups in Indian-occupied Kashmir have battled for decades for the region's independence or its merger with Pakistan and enjoy broad popular support.

The fighting has left tens of thousands dead, mostly civilians, since 1989. India has more than 500,000 troops stationed in Kashmir.

The expulsions came after a German court in early May said an Indian national will stand trial there in August accused of spying on Sikh and Kashmiri communities for New Delhi's secret service.

India is also experiencing increased friction with its other neighbours China and Nepal. India has several disputes with regional superpower China along their 3,500-kilometre (2,175-mile) border. Hundreds of Indian and Chinese troops are currently involved in the latest face-off concentrated in Ladakh region just opposite Tibet. New Delhi has turned down US President Donald Trump's offer to mediate that dispute.

The Nepalese government in mid-May drew up a new political map that includes strategically important territory it disputes with India. The new map followed protests in Nepal after its bigger neighbour inaugurated an 80-kilometre road in Uttarakhand state leading up to a disputed pass.