A high-tech Chinese research ship docked at the strategically important Hambantota port departed from Sri Lankan waters on Monday after a controversial six-day visit.

The ballistic missile and satellite tracking ship Yuan Wang 5 ship was originally scheduled to arrive at the Chinese-run port on August 11 but it was delayed in absence of permission by Sri Lankan authorities following security concerns raised by India.

The Chinese ship arrived in the southern Sri Lankan port of Hambantota on August 16 at 8:20 am local time. It was docked there for replenishment.

The ship left the port at 4 pm local time, harbour master Nirmal Silva told reporters here.

Its next port call is at China's Jiang Yin port, officials said.

The Hambantota port officials said as agreed there was no rotation of personnel during the call. Sri Lanka provided the necessary assistance sought by the Chinese embassy here during the ship's visit.

Sri Lanka had asked China to defer the visit amid India's concerns over it. On August 13, Colombo granted the port access to the vessel from August 16 to 22 on condition that it will keep the Automatic Identification System (AIS) switched on within the Exclusive Economic Zone (EEZ) of Sri Lanka and no scientific research to be conducted in Sri Lankan waters.

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

It said that no rotation of personnel would take place during the port call and the Sri Lankan government was requested to provide the necessary assistance by the Chinese Embassy in Colombo.

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

The local telecommunications regulatory authority had issued a No Objection Letter for the use of frequencies and communication equipment subject to non-interference and non-protection basis.

There were apprehensions in New Delhi about the possibility of the vessel's tracking systems attempting to snoop on Indian defence installations while being on its way to the Sri Lankan port.

China says the ship is used for scientific research, but the US Defence Department says the ship is under the command of China's People's Liberation Army (PLA) and is capable of tracking satellites and missile launches.

The ship's arrival at the Hambantota port became controversial as China leased the port from Sri Lanka in 2017 for 99 years after Colombo failed to pay debts related to the construction of the facility.

Colombo's nod to the docking of the Chinese research vessel was crucial as the cash-strapped Sri Lankan government is seeking an early bailout from the International Monetary Fund (IMF).

China is a major creditor of Sri Lanka, and is vital to Sri Lanka's efforts to restructure its debt to secure a bailout from the IMF.