China's envoy in Sri Lanka on Tuesday played down the controversy surrounding the arrival of a high-tech Chinese research ship at the southern port of Hambantota, calling such visits "very natural".

Chinese ballistic missile and satellite tracking ship Yuan Wang 5 arrived in the southern port of Hambantota at 8.20 am local time. It will be docked there till August 22.

The ship was originally scheduled to arrive at the port on August 11 but it was delayed in absence of permission by the Sri Lankan authorities.

Sri Lanka had asked China to defer the visit amid India's concerns over it. On Saturday, Colombo granted the port access to the vessel from August 16 to 22.

Sri Lanka said the security clearance was granted from the Ministry of Defence for the visit of the vessel for replenishment purposes during the stipulated period.

Qi Zhenhong, China's Ambassador to Sri Lanka, was present at the port to welcome the ship.

Several parliamentarians from the breakaway group of the ruling Sri Lanka Podujana Peramuna party were also present.

"This kind of research ship visiting Sri Lanka is very natural. In 2014 a similar ship came here," Zhenhong told reporters when asked about the visit.

Asked about the Indian concerns, the Ambassador said, "I don't know, you should ask the Indian friends."

The ship maintained a very strict security operation with no one being allowed on board.

The Sri Lankan decision to postpone the visit caused much controversy in the country as the visit had been cleared in mid-July.

Commenting on the ship's arrival, the Cabinet spokesman Bandula Gunawardena said the issue was settled amicably.

"Relations with all countries are important to us," Gunawardena said.

The security and cooperation in the neighbourhood are of utmost priority in handling the issue of the Chinese vessel Wang Yang 5, the Foreign Ministry here said in a statement.

India has traditionally taken a stern view of Chinese military vessels in the Indian Ocean and has protested such visits with Sri Lanka in the past.

The ties between India and Sri Lanka had come under strain after Colombo permitted a Chinese nuclear-powered submarine to dock in one of its ports in 2014.

China is the main creditor of Sri Lanka with investment in infrastructure. Debt restructuring of Chinese loans would be key to the island's success in the ongoing talks with the International Monetary Fund for a bailout.

India on the other hand has been Sri Lanka's lifeline in the ongoing economic crisis.

India has been at the forefront of extending economic assistance of nearly USD 4 billion to Sri Lanka during the year as the island nation is grappling with the worst economic crisis since independence in 1948.

India's concerns have been focused on Hambantota port in particular. In 2017, Colombo leased the southern port to China Merchant Port Holdings for 99 years, after Sri Lanka was unable to keep its loan repayment commitments, fanning fears over the potential use of the port for military purposes.