Memories of the day in October that changed the life of teenager Mohammed Riaz for ever come in vivid flashbacks, when it’s dark and quiet.

State forces arrived in his village in the Buthidaung township of Myanmar. Officers entered the family home, raped and killed his two elder sisters and shot his brother dead.

Mohammed, 17, and his mother managed to get out of the house. “I was so scared. It happened so quickly. Even if I wanted to rescue them, I was so scared. I wanted to do something,” he said through an interpreter.

Biplop, 18, who goes only by one name, has nightmares following an army attack on his village in the same district a month earlier. His mother and sister were held for seven hours, tied to chairs and beaten.

“The guards were all around the place. The military were going into homes,” he says. “I tried to protect my mother and sister, but they tied us up, so I couldn’t.”

From the window of his home, Biplop says he saw a man being beheaded and babies being killed. When no one is around, he cries.

About 700,000 Rohingya have fled Myanmar and crossed the border into Bangladesh since 25 August last year when renewed violence broke out in northern Rakhine state. They joined more than 300,000 Rohingya already in the country. Mohammed and Biplop, who were among the new arrivals, are now getting help to deal with the trauma.

Imrul Hosen leads a counselling session at the Balukali camp. Photograph: Tom Pilston/Action Against Hunger

“When I’m alone and want to think about anything, all these flashbacks come. I have nightmares as well,” said Mohammed, sitting inside a tent made of bamboo and tarpaulin in Balukhali, a makeshift refugee camp near the town of Cox’s Bazar.

Dressed in a traditional lungi (a type of sarong) and a white Metallica T-shirt – though he has never heard of the band – his emotions veer from anger to sadness. There is fear for his mother, who he says is constantly crying. “I don’t look forward to tomorrow,” he said.

Mohammed’s willingness to talk nevertheless offers hope for his future, said Imrul Hosen, assistant project officer for mental health with Action Against Hunger. The NGO runs stress management sessions in camp for young men like Mohammed and Biplop.

“Men don’t open up easily. It requires a lot of rapport building to make them understand that [what they say] won’t be used against them,” he said.

Hosen knows it is critical that men talk. He hopes group therapy sessions will help to stop traumatised adolescents in the camp from growing up into angry, violent young men, vulnerable to radicalisation, and prevent the onset of post-traumatic stress disorder.

The World Health Organisation estimates that up to one in five people caught up in an emergency will develop some form of depression or anxiety. Yet, in 2015, the WHO found that hardly any mental healthcare was provided by aid agencies. It has since called for mental health support to be a key part of the healthcare package offered to people forced from their homes.

Over the past 15 years there has been a growing awareness of the need for mental health support for refugees. The UN refugee agency, the UNHCR, has been developing tools that aid agencies can use.

Action Against Hunger, Médecins Sans Frontières and Save the Children are among more than 10 NGOs and aid agencies now providing mental health support to refugees in Cox’s Bazar. Their efforts, supported by the Bangladeshi government, have so far enabled almost 350,000 people to receive counselling. But men are less likely than women to put themselves forward for help.

“A lot of men, because of cultural bias, are not able to express their fears,” says Farhana Rahman Eshita, Action Against Hunger’s mental health programme co-ordinator “They feel shy or shameful to say they are feeling low. So we thought there should be specific male groups – with adolescents having separate groups – on stress management, to help them to heal and cope better with the situation.”

With the scale and speed of the influx of Rohingya refugees since August, Eshita, a clinical psychologist who counselled survivors of the Rana Plaza factory collapse in the Bangladeshi capital, Dhaka, in 2013, said agencies had to move quickly to introduce trauma counselling.

By September, her organisation had hired about 30 extra staff and was providing emergency support for women, men and children in the area. More than 20,000 boys and men have since undertaken counselling.

Eshita says that as well as the violence that men have experienced or seen, other major triggers for male anxiety and depression have included the need to adapt to a new environment, not having a job, and not knowing how they will survive and support their families.

Children at the refugee camp near Cox’s Bazar. Photograph: Tom Pilston/Action Against Hunger

That worry has been shown to translate into violence, often against wives and children. Eshita says that, for some Rohingya men, beating their wives “is normal to them, like eating and sleeping”. Stressful situations only exacerbate this tendency, but counselling provides an opportunity to discourage it, she said.

Young men attending stress management sessions with Hosen and his team at Balakuli camp meet in groups of 12 to 14 people, two or three times, to share their experiences and learn coping techniques. These include breathing exercises for when they feel anger.

Hosen said he encouraged men to continue meeting and supporting one another after the initial sessions. He also watches out for those who require more intense support and will recommend them for one-to-one counselling with a psychologist if required.

Gora Mia, 12, will be among those recommended for further support. Gora was found in a pool of blood, with a machete blow to the back of his neck, after the Myanmar military raided his village in Buthidaung last September. He had become separated from his mother and two sisters. Someone picked him up and took him across the border, and he was admitted to a hospital in Chittagong, about 180km from Cox’s Bazar, where he underwent two months of treatment.

He is now in Balakuli camp, after being reunited with his mother, Hasina Begum. She says Gora is very angry. “He keeps asking me, ‘Why did you leave me, why did other people bring me here?’”

She says Gora can’t understand why he was hurt or why he came to Bangladesh alone. “He’s angry about the whole situation, but he doesn’t know how to express it, so he cries,” she says. “I feel helpless.”

Begum doesn’t know where her husband is or how she will support herself, Gora and her daughters, one of whom has a disability.

Because of his injuries, it’s a struggle for Gora to hold his head up, and he has limited movement in his right arm. He received some treatment in Cox’s Bazar but needs more specialist care.

“I wish I could walk like before, and feel healthy,” he says beneath the tarpaulin tent, dressed in a lungi and red Twenty20 cricket top.

Biplop, whose grey T-shirt is emblazoned with the word “RAW”, perhaps reflecting his internal anguish, said talking about his experiences in the therapy sessions, and with friends, had helped. He says he feels “a little bit lighter” after having the chance to share his story.

“I understand that I can’t expect a happy free life in Bangladesh because I’m not a Bangladeshi citizen,” he said. “I think if I can go back home and things calm down and life becomes like before, maybe I have a chance to live a happy life like other people do.”