The Syrian government used controlled explosives and bulldozers to raze thousands of residential buildings, an international human rights group says.
In some cases entire districts have been flattend, in a campaign that appeared designed to punish civilians sympathetic to the opposition.
The demolitions took place between July 2012 and July 2013 in seven pro-opposition districts in and around the capital, Damascus, and the central city of Hama, according to a 38-page report by Human Rights Watch. The New York-based group said the deliberate destruction violated international law, and called for an immediate end to the practice.
"Wiping entire neighbourhoods off the map is not a legitimate tactic of war," said Ole Solvang, emergencies researcher for HRW. "These unlawful demolitions are the latest additions to a long list of crimes committed by the Syrian government."
Human Rights Watch said many of the demolished buildings were apartment blocks, and that thousands of families have lost their homes because of the destruction.
It said government officials and media have described the demolitions as part of urban planning or an effort to remove illegally constructed buildings. But HRW said military forces of president Bashar Assad supervised the demolitions, which in each instance targeted areas that had recently been hit by fighting and were widely understood to be pro-opposition.
There also is no indication, HRW said, that pro-government districts have been targeted for similar controlled destruction.
The report includes satellite images of the areas before and after the demolitions, providing a window on the scale of the destruction.
Buildings in the Hama neighbourhood of Masha al-Arbaeen, a wedge-shaped district bordered by highways on three sides, are clearly visible in a photo dated September 28, 2012. In a second photo from October 13, the buildings have been pulverised into a white smudge, while the adjacent neighbourhoods remain untouched.
HRW said it based its report on 14 satellite images, interviews with 16 witnesses and owners of houses that were demolished.
"No one should be fooled by the government's claim that it is undertaking urban planning in the middle of a bloody conflict," Solvang said. "This was collective punishment of communities suspected of supporting the rebellion. The UN Security Council should, with an ICC referral, send a clear message that cover-ups and government impunity won't stand in the way of justice for victims."