What is the India-Pakistan conflict at sea about? | Explained

The story so far:

A Pakistan Navy vessel, PNS Hunain, collided with an Indian Navy warship, INS Kolkata, in the North Arabian Sea on September 15 after, according to India, the Pakistani ship made a dangerous overtaking manoeuvre at high speed. India summoned Pakistan’s Charge d’Affaires and cited violations of Article 10 of the 1991 India-Pakistan agreement, which requires naval vessels to maintain separation of three nautical miles. Pakistan rejected India’s allegations. INS Kolkata suffered no major damage and remains at sea. PNS Hunain was damaged and subsequently returned to harbour.

What are INS Kolkata and PNS Hunain?

The two vessels involved are different classes of warships. 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 164-metre-long warship has a full-load displacement of about 7,400 tonnes and is capable of sailing at 30-knot speed. It was commissioned into the Indian Navy in August 2014. INS Kolkata is designed primarily as a high-end surface combatant, with long-range air-defence, anti-surface, and anti-submarine capabilities. The class is equipped to operate helicopters and carries the BrahMos supersonic cruise missile as its principal anti-surface strike weapon.

PNS Hunain (F-273) is an offshore patrol vessel. It was built by Damen Shipyards in Romania and commissioned in July 2024. It is the first of Pakistan’s larger OPV 2600-based follow-on vessels to the Yarmook-class patrol ships. Damen says the OPV 2600 design is intended for maritime security and military operations, including sustained operations in contested environments. It is approximately 98 metres long, has a displacement of about 2,600 tonnes, and is capable of speeds of up to about 24 knots. Its role includes maritime surveillance, patrol and security missions. Pakistan describes the vessel as a multi-purpose platform equipped with electronic-warfare, anti-ship and anti-air warfare capabilities, as well as self-protection and terminal defence systems. It can also embark a multirole helicopter.

What does India say happened?

According to the Indian account, INS Kolkata was conducting routine surveillance when PNS Hunain approached at high speed and manoeuvred dangerously close to the Indian ship. On September 18, a spokesperson of the Ministry of External Affairs said India had examined Pakistan’s response to the diplomatic protest and rejected its allegations. He said the Pakistani ship had conducted a “dangerous overtaking manoeuvre” that resulted in the collision.

India has maintained that the manoeuvre violated both the 1991 bilateral agreement and the International Regulations for Preventing Collisions at Sea. The Ministry said INS Kolkata suffered no major damage and remained deployed at sea.

Pakistan has given a different account, alleging that the Indian warship carried out a provocative manoeuvre during the encounter. The precise sequence of movements immediately before the collision therefore remains disputed.

What is Article 10 of the 1991 India-Pakistan agreement?

Article 10 of the Agreement between India and Pakistan on Advance Notice on Military Exercises, Manoeuvres and Troop Movements, signed on April 6, 1991, lays down a specific maritime safety provision. It states that naval ships and submarines of the two countries should not approach within three nautical miles of each other while operating in international waters, “so as to avoid any accident.” Three nautical miles is about 5.6 km.

The provision is part of a broader military confidence-building framework intended to reduce the risk of miscalculation between the two countries. It is a bilateral requirement, not a universal international maritime rule applicable to warships of all countries.

Has this happened before?

The September 2026 incident is the second reported India-Pakistan naval collision involving the 1991 framework. In June 2011, Pakistani warship PNS Babur came close to Indian Navy frigate INS Godavari during anti-piracy operations in the Gulf of Aden, causing minor damage. India lodged a protest, citing navigational-safety violations.

What happens next?

India has summoned Pakistan’s Chargé d’Affaires in New Delhi and lodged a strong protest. It has also instructed its Charge d’Affaires in Islamabad to raise the matter with Pakistan’s Foreign Ministry.

New Delhi has advised Pakistan to ensure that its military units exercise due care and comply with relevant bilateral agreements to prevent a recurrence. The fact that the collision occurred in international waters does not place the two navies outside agreed rules of conduct.

For now, the key unresolved question is the exact sequence of manoeuvres that brought the two vessels into close proximity.