Border Guard Bangladesh personel detain a suspected Myanmar citizen (C), who is suspected by Rohingya escapees of spying for Myanmar, at a refugee camp in Teknaf in southern Cox's Bazar district on November 24, 2016. Dhaka has called on Myanmar to take 'urgent measures' to protect its Rohingya minority after thousands crossed into Bangladesh in just a few days, some saying the military was burning villages and raping young girls.

At least 21 insurgents and 11 members of the security forces were killed in Myanmar's troubled Rakhine state on Friday when militants staged a major coordinated attack on 24 police posts and an army base, the military said.

The fighting - still going on in some areas - marked a major escalation in a simmering conflict in the northwestern state since last October, when similar attacks prompted a big military sweep beset by allegations of serious human rights abuses.

The Arakan Rohingya Salvation Army (ARSA), a group previously known as Harakah al-Yaqin, or "Faith Movement", which instigated the October attacks, claimed responsibility for the early morning offensive, and warned of more attacks.

The treatment of approximately 1.1 million Muslim Rohingya has emerged as majority Buddhist Myanmar's most contentious human rights issue as it makes a transition from decades of harsh military rule.

It now appears to have spawned a potent insurgency, which has grown in size and morphed from an militant group into something more akin to a widespread movement, observers say.

The situation in the state deteriorated early this month when security forces began a new "clearance operation" in a remote mountain area.

The army said that one soldier, 10 police and 21 insurgents had been killed in the attacks. Two military sources contacted by Reuters said there may be more deaths.

"In the early morning at 1 a.m., the extremist Bengali insurgents started their attack on the police post ... with the man-made bombs and small weapons," said the army, referring to the Rohingya with the derogatory term implying they are interlopers from Bangladesh.

It added the militants also used sticks and swords and destroyed bridges with explosives. Further attacks came at around 3 a.m. and 4 a.m., it said.