Myanmar's government said on Friday a group inspired by Islamist militants was behind attacks on police border posts in its ethnically riven northwest, as officials said they feared a new insurgency by members of the Rohingya Muslim minority.

The sudden escalation of violence in Rakhine state poses a serious challenge to the six-month-old government led by Aung San Suu Kyi, who was swept to power in an election last year but has faced criticism abroad for failing to tackle rights abuses against the Rohingya and other Muslims.

A statement from the office of Myanmar's President Htin Kyaw blamed the little-known "Aqa Mul Mujahidin" for recent attacks around Maungdaw Township, a mainly Muslim area near the frontier with Bangladesh.

"They persuade the young people using religious extremism, and they have financial support from outside," said the Burmese language statement.

"They are broadcasting their videos on the Internet like ISIS, Taliban and al Qaeda. They now have 400 insurgents fighting in Maungdaw region."

Several videos showing armed men speaking the language of the mostly stateless Rohingya have circulated online this week. Reuters has not been able to verify the authenticity of the videos, but government officials say they believe they show the perpetrators of the attacks that began on Oct. 9.

The 1.1 million Rohingya living in Rakhine state face discrimination, severe restrictions on their movements and access to services, especially since inter-communal violence in 2012 that displaced 125,000 people.

The Rohingya are not among the 135 ethnic groups officially recognised in Myanmar, where many in the Buddhist majority regard them as illegal immigrants from Bangladesh.

Suu Kyi, who is barred from the presidency by the constitution but leads Myanmar's first democratically elected government in decades as "State Counsellor", has appointed former United Nations chief Kofi Annan to head a panel to propose solutions to Rakhine state's problems.

NEW KIND OF CONFLICT

Information Minister Pe Myint, who visited Maungdaw Township this week, said the dramatic escalation in violence "may affect the work we've been doing for Rakhine State".

"Previously there has been riots and conflict between the communities. Now there is armed conflict," he told reporters in the state capital, Sittwe, on Friday. "The nature of the conflict has changed."

Officials have said hundreds of men - some armed with automatic weapons and others with sticks and swords - launched coordinated assaults against three border posts in the early hours of Oct. 9, killing nine police officers and wounding five.

In response, the military has poured troops into northern Rakhine State to search for attackers, who made off with dozens of weapons and more than 10,000 rounds of ammunition.

Suu Kyi has told security forces to use caution and follow the law in their response. Her civilian administration does not have oversight over the powerful military, which has designated the area an "operation zone".

At least 26 people have been killed by security forces in what state media described as skirmishes with armed attackers and in which four soldiers were also killed.

Human rights groups say they have evidence that extrajudicial killings may have taken place.

Researchers and aid workers in Rakhine State have consistently reported that the vast majority of Rohingya have no interest in resorting to violence.

"We don't appreciate terrorism. It's not the solution," said Kyaw Hla Aung, a Rohingya community leader in Sittwe.

MILITANT LINKS

The statement from the Myanmar president's office said interrogations with suspects captured after the attacks had revealed links with militants in Pakistan.

The ringleader was a 45-year-old who has lived in Bangladesh and spent six months training with the Pakistani Taliban, it said.

The statement added that the Aqa Mul Mujahidin - the name of which could not be found in any previous news reports online - was linked to the Rohingya Solidarity Organisation (RSO), an armed group that has long been assumed defunct.

The military-run newspaper Myawady had earlier said soldiers had recovered "RSO flags and RSO badges" in Maungdaw.

In one of the videos posted online, a man dressed in black calls for "the Rohingya Muslims in Rakhine to all come out and join the jihad", according to Reuters' translation.

In a second video, the same man appears to reference the Myanmar military's helicopters, which have been hunting the attackers, as he encourages the armed men surrounding him to welcome martyrdom.

A third video shows a long column of men armed with swords and rifles marching in damp, rugged terrain.

The weapons in the videos match those taken from border police, officials said.

The possible emergence of an insurgency involving Rohingyas has already been seized upon by Buddhist nationalists.

Wirathu, a Buddhist monk known for his anti-Muslim preaching, has posted graphic images of the slain police on Facebook.