An Indian Navy warship and a Pakistan Navy vessel collided in the North Arabian Sea on September 15, according to accounts that the two countries dispute.

India said the Pakistan Navy vessel PNS Hunain made a dangerous overtaking manoeuvre at high speed, leading to the collision with the Indian Navy warship INS Kolkata. India summoned Pakistan's Charge d'Affaires over the incident and cited a violation of Article 10 of the 1991 India-Pakistan agreement, which requires naval vessels to maintain a separation of three nautical miles.

Pakistan rejected India's allegations. The two sides have given contrasting accounts of what happened.

According to the account provided, INS Kolkata suffered no major damage and remains at sea. PNS Hunain was damaged and subsequently returned to harbour.

The two vessels involved are different classes of warship. INS Kolkata is the lead ship of the Indian Navy's Project 15A Kolkata-class guided missile destroyers, built by Mazagon Dock Shipbuilders in Mumbai.

The incident is notable because it involves the navies of two countries that have an existing agreement setting out rules for naval vessels operating in proximity, and because it prompted a formal diplomatic demarche by India.