Burma's president has acknowledged major destruction in the west of the country, scene of recent ethnic unrest.
"There have been incidents of whole villages and parts of the towns being burnt down in Rakhine state," Thein Sein's spokesman told the BBC.
He was speaking after Human Rights Watch released satellite pictures showing hundreds of buildings destroyed in the coastal town of Kyaukpyu alone.
It says the victims were mostly Muslim Rohingya, targeted by non-Muslims.
Presidential spokesman Zaw Htay told the BBC the government was tightening security in Rakhine state, which is also known as Arakan.
"If necessary, we will send more police and military troops in order to get back stability," he added.
There is long-standing tension between ethnic Rakhine people, who make up the majority of the state's population, and Muslims, many of whom are Rohingya and are stateless.
The Burmese authorities regard the Rohingya as illegal immigrants and correspondents say there is widespread public hostility to them.
The satellite pictures released by Human Right Watch, a US-based group, show Kyaukpyu district on 9 October, and then on 25 October.
On 9 October, hundreds of closely packed houses can be seen on the peninsula, as well as scores of houseboats along the northern shoreline.
But in the image taken on Thursday, few boats remain and the 35-acre district is almost entirely empty of houses.
HRW said many residents are thought to have fled by boat.
A local reporter who visited the site told the BBC's Burmese service the area had been completely destroyed, with some buildings still smouldering.
At least 64 people were killed this week, officials said, in the first serious outburst of violence since June, when a state of emergency was declared in Rakhine.
At that time deadly clashes claimed dozens of lives and thousands of people were forced to flee their homes - many are yet to return.
HRW said it feared the death toll from the latest unrest could be much higher, based on witness reports and "the government's well-documented history of underestimating figures that might lead to criticism of the state".
Non-Muslims are reporting that this time they too were fired on by government forces during the unrest, and suffered many casualties.
The government has declared a curfew in the affected areas, but its response since the violence first broke out is being widely criticised as inadequate, says the BBC's Jonathan Head in Bangkok.
On Friday six towns were hit by clashes and a night-time curfew is in place in several locations including Min Bya and Mrauk Oo where the latest spate of violence began.
It is unclear what prompted the latest clashes. The Rakhine Buddhists and Muslims, believed to be mainly Rohingya, blame each other for the violence.
In Bangladesh, border officials said they believed several boats with Rohingyas on board were waiting to try to cross the river from Burma. One official said 52 Rohingya had been sent back in the last few days.
Muslims throughout Burma have abandoned plans to celebrate the festival of Eid al-Adha because of the violence.
In August, Burma set up a commission to investigate the violence between Buddhists and Muslims in the west of the country. Authorities earlier rejected a UN-led inquiry.