Image copyright Reuters Image caption There is a heavy military presence in Rakhine state

Attacks by militants on police posts in Myanmar's Rakhine state have left 71 people, including 12 security personnel, dead, the authorities say.

More than 20 posts were targeted by Muslim militants in pre-dawn raids, the government said, in Rakhine's worst violence for months.

Rakhine has been hit by clashes between Muslim and Buddhist communities.

The attacks come a day after a report warned more people would be radicalised if ethnic tensions were not addressed.

Rakhine state, in western Myanmar, is home to more than a million Rohingya Muslims.

Tensions with the majority Buddhist population have been rumbling for years, and tens of thousands of Rohingya have fled to Bangladesh, accusing Myanmar authorities of ethnic persecution.

A government statement said that "extremist Bengali insurgents attacked a police station in Maungdaw region in northern Rakhine state with a handmade bomb explosive and held co-ordinated attacks on several police posts at 01:00".

The government uses the term "Bengali" to describe the stateless Rohingya, because it maintains they are illegal immigrants from Bangladesh.

The government said one soldier, one immigration officer, 10 policemen and 59 militants were killed in the fighting. As many as 150 militants are said to have been involved.

One resident in Maungdaw told AFP news agency on Friday that they could still hear shooting and were afraid to leave the house.

Bangladesh's border guard service says it has sent back 350 Rohingya who have tried to cross into Bangladesh since the raids. It also said security was being increased along the border in the wake of the attacks.

This is the most significant outbreak of violence in Rakhine since October 2016, when nine policemen died in similar attacks on border posts. The government said they were carried out by a previously unknown Rohingya militant group.

The attacks triggered a military crackdown that led to widespread allegations of killings, rape and torture of Rohingya, and an exodus of Rohingya into Bangladesh. The UN is currently investigating alleged human rights abuses by the security forces, who deny wrongdoing.

Rakhine is the poorest state in Myanmar, the UN says. Many Rohingya are living in refugee camps in the wake of waves of communal violence, and there is deep mistrust between Buddhist and Muslim communities.

On Thursday, former UN chief Kofi Annan warned in a report that a "calibrated response" combining political, security and economic initiatives was needed in Rakhine state to reduce ethnic tensions and prevent more violence.

In a statement on Friday he condemned the attacks and said they showed "a worrying escalation of violence".