The Burmese authorities may have killed more than 1,000 Rohingya Muslims during a recent crackdown on the minority group in the northeast Rakhine state, two unnamed UN officials have told the Reuters news agency.

Authorities in Burma launched a military campaign against the Rohingya after militant elements of the group were accused of attacking police border posts in October last year.

The government accepts it has killed some Rohingyas in the crackdown but denies allegations of atrocities against civilians, including claims that women and children have been raped and murdered.

The two UN officials, who Reuters said were senior members of different agencies involved in monitoring the human rights situation in Burma, said they were concerned the scale of the casualties had not been grasped by the outside world.

"The talk until now has been of hundreds of deaths," one was quoted as saying. "This is probably an underestimation - we could be looking at thousands."

Myanmar's presidential spokesman, Zaw Htay, said the latest reports from military commanders were that fewer than 100 Rohingya militants have been killed in a counterinsurgency operation.

Asked about the UN officials' comments that the death toll could be over 1,000, he said: "Their number is much greater than our figure. We have to check on the ground."

Earlier, Pope Francis issued a strong defence of the Rohingya Muslims' right to live free from persecution. In a stinging attack on the Burmese regime, the Pope said the Rohingyas have been tortured and killed “simply because they want to live their culture and their Muslim faith”.

Pope Francis made his comments during an unprepared section of his weekly address. He appeared to be referring to a UN rights office “flash report”, issued last week, detailing allegations of abuse, rape and murder of Rohingyas at the hands of the Burmese military.

The UN has previously dubbed the Rohingyas, who are also denied access to university education and in 2013 were hit with a two-child policy, as “the most oppressed people on Earth”.

"Pope Francis' comments should serve as a wake up call to the international community," Charu Lata Hogg, an associate fellow with the Asia Programme at Chatham House, told The Independent.

"Despite the scathing UN report and the stream of NGO reporting on the plight of the Rohingyas, there doesn't seem to have been much international condemnation.