Hundreds more Rohingya refugees remain stuck at sea, rights groups have warned, just one day after it emerged that dozens of people died onboard a boat that was refused entry to Malaysia and left adrift for two months.

On Friday, Malaysia’s air force confirmed it had denied entry to a second boat carrying about 200 Rohingya people, claiming it had done so to prevent further spread of the coronavirus within the country, which remains under lockdown.

Researchers believe other boats are likely to also be stuck at sea, packed with refugees who are attempting to escape desperate and squalid conditions in the city of Cox’s Bazar in Bangladesh.

Refugee camps on the border of Bangladesh grew to be some of the biggest in the world following a brutal military crackdown in 2017 that forced more than 700,000 Rohingya to flee Myanmar.

Amnesty International said it had received information about as many as five boats spotted off the coasts of Malaysia and southern Thailand in recent days, believed to be carrying hundreds of people.

It is feared that the refugees could remain trapped at sea and unable to disembark as countries cite the spread of Covid-19 as a justification for turning boats back.

Q&A Who are the Rohingya and what happened to them in Myanmar? Show Described as the world’s most persecuted people, 1.1 million Rohingya people live in Myanmar. They live predominately in Rakhine state, where they have co-existed uneasily alongside Buddhists for decades. Rohingya people say they are descendants of Muslims, perhaps Persian and Arab traders, who came to Myanmar generations ago. Unlike the Buddhist community, they speak a language similar to the Bengali dialect of Chittagong in Bangladesh. The Rohingya are reviled by many in Myanmar as illegal immigrants and suffer from systematic discrimination. The Myanmar government treats them as stateless people, denying them citizenship. Stringent restrictions have been placed on Rohingya people’s freedom of movement, access to medical assistance, education and other basic services. Violence broke out in northern Rakhine state in August 2017, when militants attacked government forces. In response, security forces supported by Buddhist militia launched a “clearance operation” that ultimately killed at least 1,000 people and forced more than 600,000 to flee their homes. The UN’s top human rights official said the military’s response was "clearly disproportionate” to insurgent attacks and warned that Myanmar’s treatment of its Rohingya minority appears to be a "textbook example” of ethnic cleansing. When Aung San Suu Kyi rose to power there were high hopes that the Nobel peace prize winner would help heal Myanmar's entrenched ethnic divides. But she has been accused of standing by while violence is committed against the Rohingya. In 2019, judges at the international criminal court authorised a full-scale investigation into the allegations of mass persecution and crimes against humanity. On 10 December 2019, the international court of justice in The Hague opened a case alleging genocide brought by the Gambia. Rebecca Ratcliffe Photograph: Tracey Nearmy/AAP

The developments are reminiscent of a 2015 crisis when many Rohingya died at sea after south-east Asian nations refused entry, prompting the UN to warn that people were being left stranded on “floating coffins”.

On Thursday, Bangladesh rescued almost 400 people in the Bay of Bengal, after they spent two months adrift. They had attempted to sail to safety in Malaysia, survivors reported, but were refused entry. Dozens of those onboard had died.

On the same day, it has since emerged, another Rohingya boat was intercepted by two Malaysian navy vessels after it was spotted by an air force jet off the north-western island of Langkawi. Malaysian sailors gave the refugees food before escorting them out of the country’s waters, the air force said.

“With their poor settlements and living conditions ... it is strongly feared that undocumented migrants who try to enter Malaysia either by land or sea will bring [Covid-19] into the country,” the air force said in a statement late on Thursday.

It added that “maritime surveillance operations will be intensified”.

Chris Lewa, of the Arakan Project, which works on Rohingya rights issues, said that Covid-19 was not an acceptable reason for any country to refuse entry to refugees.

“The duty of the navy is to rescue people at sea, not to push them out and put their life at risk even more,” she said. “What is going to happen? Where are these people going to go?”

The refusal of entry to Malaysia is a worrying sign that the country is becoming increasingly hostile to Rohingya refugees.

While relatively few boats carrying Rohingya have arrived in Malaysia since the 2015 crisis, some have been allowed in. Earlier this month, 202 Rohingya people landed in Langkawi and were detained.

In a statement, Amnesty International called on Malaysia and Thailand to “immediately dispatch search and rescue boats with food, water and medicine to meet the urgent needs of possibly hundreds still at sea”.

Both countries should urgently allow the people to disembark safely, the group said, adding: “Both Thailand and Malaysia are aware that people’s lives are in danger. Refusing to help the people on these boats would not be wilfully blind – it would be consciously making their plight even worse.”

Agence France-Presse contributed to this report