By Anbarasan Ethirajan BBC News

The expected arrival of a Chinese research ship in the Maldives this week has escalated tensions between Beijing, Delhi and Male.

Officially, the vessel Xiang Yang Hong 3 is there to “make a port call, for rotation of personnel and replenishment”. In short, an entirely innocuous stop.

But that is not how it is being seen in Delhi. Instead, the ship’s presence is at the very least a diplomatic snub. At worst, some fear, it could be a mission to collect data which could – at a later date – be used by the Chinese military in submarine operations.

China experts, however, have shrugged off their concerns.

“The Chinese ships carry out scientific research work in the Indian ocean. Its activities on the high sea are entirely legitimate,” Zhou Bo, a former People’s Liberation Army Senior Colonel, told the BBC.

“Sometimes the ships need replenishment – like fuel, food and water. So, they berth in a third country port, which is normal. So, the Indian government shouldn’t make any fuss about it. Indian Ocean is not India’s Ocean,” asserted Mr Zhou, who is now with the Tsinghua university in Beijing.

But this is not the first time that China – which competes for influence with Delhi in the Indian Ocean amid a long-standing dispute over their Himalayan border – has sent one of its ships sailing close to Indian waters.

Two Chinese naval submarines made a port call to Colombo in 2014 and two Chinese research vessels visited Sri Lanka, close to the tip of southern India, in the past two years, much to the displeasure of India.

The arrivals came as China, which has loaned billions of dollars to Colombo, made significant inroads into Sri Lanka.

The research ship, Xiang Yang Hong 3, had in fact originally planned to visit Colombo for replenishment before proceeding to the Maldives. But that has been shelved for now, according to Tharaka Balasuriya, the junior foreign minister of Sri Lanka.

“During this one year we want to develop our technology and expertise so that we can join in these research activities on an equal basis,” he told the BBC.

However, Colombo’s decision to stop the research vessels is being seen as a response to India’s strong objections to such visits by Chinese vessels.

• Maldives ultimatum on troops deepens row with India

India’s objections however, have made little difference in the Maldives.

The Maldives, which consists of about 1,200 coral islands and atolls in the middle of the Indian Ocean, has long been under India’s sphere of influence. But Mohamed Muizzu, who took over as president in November and is regarded as pro-China, wants to change that.

He campaigned on an ‘India Out’ platform, asking Delhi to withdraw about 80 Indian military personnel based on the island. India says the troops are in the island nation to maintain and operate three reconnaissance and rescue aircraft, donated by Delhi years ago.

The Maldivian government has set an ultimatum to Delhi to withdraw its troops by 15 March, two days before the country’s parliamentary polls.

Following talks in Delhi last week, the Maldivian foreign ministry said India had agreed “to replace the military personnel” and that the first batch will leave by 10 March and the rest by the second week of May.

In December, Mr Muizzu’s administration also announced that it would not renew a hydrographic survey agreement with India that was signed by the previous government to map the seabed in the Maldivian territorial waters.

Relations have in fact deteriorated so much that none of the senior leaders of the Maldivian government attended a recent event organised by the Indian High Commission in Male to mark India’s 75th Republic Day.

China, meanwhile, rolled out the red carpet to Mr Muizzu when he went on a five-day state visit to Beijing last month. Since that trip, high-level Chinese officials have visited the Maldives. Mr Muizzu has also announced several Chinese-funded infrastructure projects.

The sudden shift in Male’s position towards China has raised concerns in Delhi, which attaches strategic significance to the island nation.

China, with its rapidly expanding naval forces, would likely also want access to such a strategically important location – something India wants to prevent.

“Of course, the Maldives is very important; it is the southern Oceanic flank of India,” Shyam Saran, a former Indian foreign secretary, told the BBC.

“Just like we had serious reservations about what was happening in Sri Lanka, we will have serious reservations about that may happen in the Maldives,” Mr Saran said.

But it is not just Delhi worried about the relationship with Male.

The opposition Maldivian Democratic Party (MDP) and others have been urging Mr Muizzu’s government for a course correction, saying it’s not in the country’s interests to antagonise a giant neighbour like India. Last week the MDP said it was even contemplating moving impeachment proceedings against Mr Muizzu.

As a small island nation, the Maldives depends on India for most of its food, infrastructure building, and technological advancement. Many Maldivians go to India for medical treatment.

• Maldivians debate India’s ‘boycott’ of their nation

“Most people here think that government has taken the hostility against India a bit too far and that it is totally unnecessary,” Aik Ahmed Easa, a lawyer in Male affiliated with the opposition MDP, told the BBC.

“The Maldives is a small country. But this is going into a dangerous phase where we are getting into the middle of the Asian superpower rivalry,” he said.

The Maldivian President’s office and the foreign minister did not respond to requests for comment.

China has greater strategic ambitions and it’s likely to send more ships to the Indian Ocean region for oceanographic research or to protect its commercial interests, experts say. For India, the challenge will be how to counter Beijing’s growing assertive influence in an area that Delhi perceives as its backyard.

Mr Zhou says Chinese aircraft carriers and their support vessels will eventually reach the Indian Ocean. If India disrupts restocking supplies for these ships in a third country – like Sri Lanka – then Beijing will be “furious”, he says.