Human Rights Watch (HRW) on Monday urged Myanmar to investigate the failure of police to stop a recent wave of Buddhist-Muslim killing and arson attacks.
The New York-based rights watchdog released satellite images which it said showed more than 800 buildings were totally destroyed in the central town of Meiktila, leaving several charred areas where homes and properties once stood.
"The government should investigate responsibility for the violence in Meiktila and the failure of the police to stop wanton killings and the burning of entire neighborhoods," said HRW Asia director Brad Adams.
Last month's unrest, which later spread to several other towns, has left 43 people dead and more than 1,300 homes and other buildings destroyed, according to state media in the former army-ruled nation.
According to the United Nations, about 12,000 people have been displaced.
The worst-hit areas in Meiktila are believed to be neighbourhoods once home to "a significant number of Muslims", said HRW deputy Asia director Phil Robertson.
The violence "was allowed to run for days on end", he told AFP. "There's been plenty of information that we found, and that others have reported, of essentially the police allowing it to go on and not intervening."
HRW said the destruction bore similarities to sectarian unrest in a different area in western Myanmar last year that killed at least 180 people and left "large, clearly defined residential areas in ashes".
The situation appears to have calmed since President Thein Sein on Thursday vowed a tough response against those behind the violence, which he attributed to "political opportunists and religious extremists".
In a radio address on Sunday, the former general appealed to members of the Buddhist clergy to "assist the government in promoting peace and stability".
Some monks were involved in the recent violence, according to witnesses, while others have spearheaded a move to shun shops owned by Muslims.
Security forces have fired warning shots in some instances to disperse rioters, but they have also faced criticism from Muslim leaders in the Buddhist-dominated country for failing to stop attacks.
Last year HRW accused local security forces of killing Muslim villagers in the western state of Rakhine while government troops "stood by and watched".