Sri Lanka has granted 48 hours for a Chinese vessel to conduct marine research off the island's west coast under supervision, the foreign ministry said Sunday, despite Indian concerns that it could be a spy ship.

Ministry spokesperson Kapila Fonseka said Chinese research ship Shi Yan 6, which has been in Colombo since Wednesday, would be allowed to carry out work for two days starting Monday.

Earlier, Sri Lanka allowed the vessel to enter the main port of Colombo only for "replenishments" over concerns raised by neighboring India that the craft could be used to spy against them.

New Delhi is suspicious of China's increasing presence in the Indian Ocean and its influence in Sri Lanka, which is strategically placed halfway along key east-west international shipping routes.

A spacecraft-tracking Chinese vessel last year raised security concerns from India, and Sri Lanka prohibited it from undertaking any research activities while in its waters.

Fonseka said local scientists will be onboard Shi Yan 6 during two days of research activities along the western seaboard of the island.

"Apart from our scientists and researchers, the Sri Lanka navy too will be monitoring this vessel," Fonseka told Agence France-Presse.

The 90-meter vessel is anchored at the Colombo harbor where a Chinese state-run company operates a deep sea terminal.

A pair of Chinese submarines docked there in 2014, raising protests from India.

There was no immediate comment from either the Chinese or Indian diplomatic missions in Sri Lanka after Colombo granted limited approvals to Shi Yan 6.

Chinese state broadcaster CGTN calls the Shi Yan 6 a "scientific research vessel" with a crew of 60 to conduct oceanography, geology and marine ecology tests.