Syrian authorities have deliberately demolished thousands of homes for no apparent military objective but to punish civilians, a New York-based advocacy group says.

A report by Human Rights Watch uses before-and-after satellite imagery, along with witness testimony, to document the scale of destruction in major Syrian cities.

The report concludes that great swathes of districts in the capital city Damascus and the central city of Hama have been completely levelled using bulldozers and explosives.

Human Rights Watch says it recorded the destruction of 145 hectares of land in seven different cases during the past two years, an act it says is a war crime.

It names the districts as Masha'a al-Arbaeen and Wadi al-Jouz in Hama, and Qaboun, al-Tadamon, Barzeh, Harran al-Awamid and Mezze airport in and around Damascus.

It says eyewitness reports and online videos suggest the Syrian government is responsible, and the demolition is collective punishment of communities suspected of supporting the rebellion.

Syria says demolitions removed illegal buildings

Human Rights Watch cites Syrian officials and pro-government media as saying the demolitions were conducted to remove buildings constructed without the necessary permits or as part of urban planning efforts.

But it said "the context and circumstances" of the destruction showed it was actually intended to punish civilians living in areas that had previously housed rebel fighters.

It said the demolitions often occurred after government forces had cleared an area of rebels and in some cases extended several kilometres away from military or strategic locations which the authorities might be justified in protecting.

It said the destruction violated internationally recognised laws of war forbidding combatants from targeting civilians, and said Syrian authorities should be held accountable.

"No-one should be fooled by the government's claim that it is undertaking urban planning in the middle of a bloody conflict," said Ole Solvang, a Human Rights Watch researcher.

"This was collective punishment of communities suspected of supporting the rebellion."

UN chides Syria for delays in removing chemical weapons

Meanwhile, the United States has told Syria to take immediate actions to comply with a UN resolution to remove its chemical weapons materials.

The US says demands by Damascus for additional equipment are "without merit" and delays are adding to costs.

A statement by the United States, to the world's chemicals weapons watchdog in The Hague, said just 4 per cent of the chemicals declared by Syria had been removed.

"Syria has said that its delay in transporting these chemicals has been caused by 'security concerns' and insisted on additional equipment - armoured jackets for shipping containers, electronic countermeasures, and detectors for improvised explosive devices," spokesman Robert Mikulak said in the statement to the Organisation for the Prohibition of Chemical Weapons (OPCW).

"These demands are without merit, and display a 'bargaining mentality' rather than a security mentality."

Hagel asks Russia for assistance in getting Syrian compliance

US defence secretary Chuck Hagel says he discussed the issue in a call on Wednesday with his Russian counterpart, defence minister Sergei Shoigu, and asked him to "do what he could to influence the Syrian government to comply with the agreement that has been made" for destroying the chemical weapons.

Last year's chemical weapons deal appeared to provide Syria with a last-minute reprieve from possible Western military action that would have been launched in response to a major chemical attack last August.

Mr Hagel said the US ship Cape Ray, which was specially equipped to dispose of Syria's chemical weapons at sea, left a US port earlier this week.

"We believe that this effort can continue to get back on track even though we're behind schedule, but the Syrian government has to take responsibility for fulfilling its commitment that has been made," he said.

ABC/Reuters