A Chinese submarine docked in Pakistan for the first time ever last month.

According to numerous Indian media outlets, a People’s Liberation Army Navy conventional Yuan-class 335 submarine docked in Karachi, Pakistan on May 22. The reports said that the ship received replenishments for about a week inside the port. The submarine had a crew of about 65 sailors, according to the reports.

The news was first reported by India Today.

India Today also noted that the Yuan-class submarine is “equipped with torpedoes, anti-ship missiles and an air-independent propulsion that dramatically enhances its underwater endurance.”

This is not the first time that Chinese submarine deployments have rattled India in recent months. A Song-class diesel-electric attack docked in Colombo, Sri Lanka last September, greatly irking New Delhi. Just a few weeks later, a second Chinese submarine docked in Sri Lanka as well.

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Around the same time, China reportedly informed India that its Type-093 Shang-class nuclear-powered attack submarines would begin patrolling the Indian Ocean. This raised fears in New Delhi that China could try to blockade the Indian coastline using nuclear-powered submarines.

Besides Chinese submarines patrolling the Indian Ocean, which Delhi sees as its natural domain, China has also angered India by potentially selling Pakistan advanced submarines. As The National Interest previously reported, China has allegedly promised to sell Pakistan eight submarines over the next few years.

Indian media reports this week indicate that Beijing may be trying to sell Islamabad Yuan-class submarines, the same kind that docked in Karachi port last month. This raises the possibility that the submarine replenished in Karachi in order to give the Pakistani Navy a chance to inspect the submarines they may someday operate.

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Still, its undeniable that Chinese submarines are conducting longer patrols as of late, including throughout the Indian Ocean. In doing so, they seem to be following what many outside observers have defined as China’s “String of Pearls” strategy. This strategy uses Chinese built ports throughout the greater Indian Ocean in order to expand the Chinese Navy’s forward presence. A good example is the Colombo port, which Chinese companies invested in and helped build.

India has been scrambling to try to thwart this strategy. Indeed, likely caving to Indian pressure, the Sri Lankan government appeared to rule out future Chinese submarine visits to its country. Speaking in Beijing this spring, Mangala Samaraweera, Sri Lanka’s foreign minister, said:

“I really don’t know under which sort of circumstances that led to some submarines… to [visit] the port of Colombo on the very day the Japanese Prime Minister was visiting Sri Lanka. But we will ensure that such incidents, from whatever quarter, do not happen during our tenure.”

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Still, India is unlikely to pressure Pakistan to forbid Chinese submarines from docking in its ports as Islamabad and Beijing have long maintained strong ties at the expense of Delhi.

It’s worth noting that the Chinese submarine docked in Karachi just after Indian Prime Minister Narendra Modi visited China for the first time since taking his current position. Chinese provocations, usually along India and China’s disputed land borders, have often coincided with high-profile visits between their leaders.

Meanwhile, India’s undersea fleet has been in a state of disarray in recent years following a number of catastrophes, including one submarine sinking in 2013, killing many crew members on board.

However, in a rare bout of good news, India launched its first indigenously-built (French designed) attack submarine earlier this year. Ultimately, India hopes to produce six Scorpene-class diesel electric submarines.

India is also looking abroad for help with resurrecting its undersea fleet in the face of the growing Chinese submarine threat. In that regard, Japan and Germany have both indicated they’d help, among others.

Zachary Keck is managing editor of The National Interest. You can find him on Twitter: @ZacharyKeck.