At least 56 people have been killed and hundreds of homes torched since Sunday, as clashes spread in Burma's Rakhine state, officials say.
Several were killed overnight as violence erupted despite a night-time curfew in at least two towns.
The latest clashes are the first serious outburst of violence since June when a state of emergency was declared in Rakhine after 90 people were killed.
But tensions remained high between ethnic Rakhine Buddhists and Muslims.
It is unclear what prompted the latest clashes. The Rakhine Buddhists and Muslims blame each other for the violence.
Clashes erupted in the Ratha Taung township late last night but this later spread to the Kyauk Taw township, where security forces opened fire, reports say.
Rakhine state spokesman Win Myaing told BBC Burmese on Thursday that the total death toll since violence flared up again on Sunday had reached 56.
More than 1,000 houses have been torched since then and police have deployed reinforcements in the townships of Min Bya and Mrauk Oo, where curfews are now in effect.
It was the rape and murder of a Buddhist woman by three Muslims in May that set off the initial unrest.
A mob later killed 10 Muslims in retaliation, although they were unconnected with the earlier incident, and the violence escalated after that.
In June, about 90 people were killed as clashes spread across the state.
The houses of both Buddhists and Muslims were burnt down and thousands of people fled. Muslims throughout Burma have abandoned plans to celebrate the festival of Eid al-Adha because of the violence.
There is long-standing tension between the ethnic Rakhine people, who make up the majority of the state's population, and Muslims, many of whom are Rohingya. The Burmese authorities regard the Rohingya as illegal immigrants and correspondents say there is widepsread public hostility to them.
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.