India on Sunday accused Pakistani security services of "widespread harassment" outside an event hosted by the Indian embassy in Islamabad a day earlier, saying that "hundreds" of guests were turned away and some of New Delhi's diplomats were "threatened".

The allegations came after similar reports a few days earlier from New Delhi, where guests arriving at a High Commission of Pakistan event were allegedly harassed by Indian security personnel.

Similar harassment by Indian security officials had also been reported amidst Pakistan Day celebrations hosted by the High Commission of Pakistan in New Delhi in March.

According to the Indian High Commission in Islamabad, Pakistani security agencies "even used a forklift truck to remove the cars of some attendees" of the Saturday event. India said about 300 guests in total were turned away from attending Saturday's iftar dinner at the hotel.

The Indian High Commission, asking Pakistan to investigate, alleged that some of its officials and diplomats were "jostled, pushed, abused, aggressively threatened with bodily harm" and in some cases had their phones "snatched" by Pakistani security officials.

"The disappointing chain of events on June 1 not only violate basic norms of diplomatic conduct, but are against all notions of civilised behaviour," the Indian High Commission said in a statement.

Read: Indians harass guests at iftar hosted by Pakistan HC: reports

Pakistan protests against 'harassment and maltreatment' of guests in Delhi

The Foreign Office had lodged a protest against the "harassment and maltreatment" of guests that were invited for iftar by the Pakistan High Commission in New Delhi last week.

A letter by the Foreign Office dated May 31, alleged that Indian police and secret agency officials had "barricaded the High Commission from all sides. Guests were systematically channelled through the check posts, erected specially for the purpose on the day".

The Foreign Office further said: "Many Indian guests were warned of the dire consequences if they insisted on attending the function. This harassment and maltreatment of guests continued despite requests by the officials of the Pakistan High Commission.

"Kashmiri Muslims invited by the [Pakistan] High Commission were called to the police stations in their respective native areas and warned that they would be arrested and prosecuted if found in the vicinity of the High Commission in New Delhi on the day of iftar-dinner."

The Foreign Office recalled that Indian officials had behaved in a similar manner earlier this year, when Pakistan High Commission had arranged an event on Pakistan Day.

Last week, Indian publication The Tribune had reported the incident as well and said: "There may be prospects of a thaw in Indo-Pak relations, but ties at the ground level continue to be hostile, as the latest incident that occurred outside the Pakistan High Commission shows."

According to reports from New Delhi, videos had emerged of armed Indian security personnel rummaging in personal vehicles and plainclothes men asking invitees to produce identity cards that were then photographed. What was presumably another security agency was also seen writing down I-card numbers of the invitees.

Indian media had already speculated that the harassment of the High Commission of Pakistan's guests would "cast a shadow" on the iftar scheduled by Indian High Commissioner to Pakistan Ajay Bisaria on Friday "as security agencies of both countries reciprocate will full measure".

Historically tense relations between India and Pakistan plunged to dangerous levels earlier this year when the two sides carried out aerial bombing missions against each other, and even briefly fought an aerial dogfight over Kashmir skies.

Indian Prime Minister Narendra Modi afterwards swept to victory in the elections on a tough anti-Pakistan platform.

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Modi decided not to invite Prime Minister Imran Khan to last week's inauguration ceremony, in contrast to 2014, when the Indian leader had invited then-premier Nawaz Sharif to his first inauguration.