Almost 400 people have died in clashes between security forces and Rohingya Muslims in Burma, the country's military commander has said.

The numbers, posted on the military's official Facebook page, are a sharp increase on the previously reported toll of just over 100. The statement said all but 29 of the 399 dead were insurgents, whom it described as terrorists.

The statement said there had been 90 armed clashes including an initial 30 attacks by insurgents on 25 August, making the combat more extensive than previously announced.

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Advocates for the Rohingya, an oppressed Muslim minority in overwhelmingly Buddhist Burma, say hundreds of Rohingya civilians have been killed by security forces.

According to the UN, some 38,000 have fled into neighbouring Bangladesh.

It comes after Chris Lewa, director of the Arakan Project pressure group, told ABC: "So far reports—I think quite credible—mention about 130 people including women and children killed.

"That happened on Sunday when suddenly security forces cordoned [off] the whole area, together with Rakhine villagers. It seems like this has been a major massacre in Rathedaung."

The latest violence follows an attack by Rohingya insurgents on police posts in the remote region, prompting a huge military crackdown.

The insurgent group that claimed responsibility for last week's attacks, the Arakan Rohingya Salvation Army, said it acted to protect Rohingya communities.

Rohingya mothers face persecution Show all 10 1 /10 Rohingya mothers face persecution Rohingya mothers face persecution Ramida Begum holds her 10-day-old daughter in their shelter in Kutupalang, an unregistered refugee camp in Cox's Bazar, Bangladesh. 'The military caught my husband and burnt our house down a week before I left Myanmar. Since then I don't know whether my husband is dead or alive' Reuters Rohingya mothers face persecution Minara Begum sits inside the shelter, cradling her one-month-old son Ayub. Minara fled to Bangladesh from Nasha Phuru village in Myanmar with her husband and mother-in-law. 'My child doesn't get enough breast milk as I don't eat enough nutritious food. I have to buy milk powder from local market though it's not very good for my son' Reuters Rohingya mothers face persecution Amina, pictured with her 16-day-old daughter Sumaiyin, is in a refugee camp Balukhali that neighbours Ramida and Minara's. 'One and a half months ago the military came to our village and kept firing their guns. I ran away with my neighbours to save our lives. You see us alive here only because the God was so kind. They caught my uncle and my younger brother and we don't know whether they are dead or alive' Reuters Rohingya mothers face persecution Fatema sits beside her one-day-old daughter Aasma in Kutupalang. Fatema fled to Bangladesh from Jambuinna village in Myanmar two months ago after her house was burnt down by the military. She crossed Naf River by boat during the night. 'Our situation is better than many other refugees as my husband Mohammad Alom works here as a day labourer. Many of the new refugees have no work here, so they have to rely on relief' Reuters Rohingya mothers face persecution Jamalida cradles her two-month-old daughter Shahida. Jamalida came to Bangladesh with her husband from Nasha Phuru village in Myanmar Reuters Rohingya mothers face persecution Rehana Begum lays her one-day-old daughter in front of her inside their tarpaulin shelter. Rehana fled her village of Jambuinna in Myanmar three months ago. 'We were in our home and suddenly the military came to our village and started shooting. When we heard the sound of gun shots we immediately went to our relatives. We walked for four hours without any food and water to reach the border at 1 a.m. We paid 25,000 Myanmar kyat (£14) to a broker to cross.' Intercepted by Bangladesh border guards, Rehana's family narrowly escaped being sent home. 'They wanted to send us back, but then we heard gunshots from the Myanmar side and the guards released us, saying, "Stay in Bangladesh and save your lives"' Reuters Rohingya mothers face persecution Noor Begum sits next to her one-day-old daughter Sumaiya as she stares into the camera. Noor came to the camp one-and-a-half months ago from Nagpura village with her husband Jahangir Reuters Rohingya mothers face persecution Rajuma Begum observes her one-month-old son Raihan. 'I fled to Bangladesh because of fear, because I needed to save my children. I was pregnant and suffering from fever while crossing the border. I also have an 11-month-old boy, so it was very difficult to reach the border from our village Wabek in Myanmar. I had to rest frequently. After six hours of horrible walking we finally reached the border at 2am and crossed after paying a broker' Reuters Rohingya mothers face persecution Eighteen-year-old Asmot Ara rests her newly born daughter on her lap. Asmot said she came to the camp one month ago with neighbours from Nagpura village. In Myanmar her father-in-law was killed and their home burnt down by the Myanmar military Reuters Rohingya mothers face persecution As Marijaan holds her 25-day-old daughter Noor Habi, her son peers over her shoulder. Marijaan fled to Bangladesh from Khyeri Prang village in Myanmar one month ago after her house was burnt down by the Myanmar military. 'I reached the border at night and crossed by the boat. I paid the boatman to cross the Naf River' Reuters

Burma's leader, Aung San Suu Kyi has said the "terrorist" attacks were "a calculated attempt to undermine the efforts of those seeking to build peace and harmony in Rakhine state".

The Burmese government has repeatedly denied claims the Rohingya are facing genocide. It previously brushed away evidence of human rights violations as fake news and "propaganda".

Bangladeshi border guards have tried to keep out the fleeing Rohingya, but thousands could be seen on Friday making their way across muddy rice fields.

Young people helped carry the elderly, some on makeshift stretchers, and children carried newborns.

Some, carrying bundles of clothes, cooking utensils and small solar panels, said they had walked at least three days to get to the border.

Sham Shu Hoque, 34, crossed the border with 17 family members. He said he left his village of Ngan Chaung on 25 August after it was attacked by Burmese security forces who shot at the villagers. He said troops also used rocket-propelled grenades, and helicopters fired some sort of incendiary device.

Five people were killed in front of his house, he said. His family survived the attack but was told by the soldiers to leave. They took a week to reach Bangladesh, hiding in villages along the way, he said.

Most of Burma's estimated 1 million Rohingya live in northern Rakhine state. They face severe persecution, with the government refusing to recognize them as a legitimate native ethnic minority, leaving them without citizenship and basic rights.