Starvation tactics against civilians are being used as a weapon of war by the Syrian government, the human rights group Amnesty International says.
A new report says at least 128 refugees have died at the besieged Yarmouk camp in Damascus as a result.
It says thousands of people still trapped there face a “catastrophic humanitarian crisis”.
Amnesty says families have been forced to forage for food in the streets – risking being killed by snipers.
There were reports of fresh fighting on the edge of the camp last week.
Activists said at least seven people were killed in the blast
Several people have been killed and wounded in an explosion in the Syrian capital, Damascus, Syrian state TV reports.
The state new agency Sana said a “terrorist bombing” attack had taken place in the Tadamon district in the south of the capital.
Tadamon has been a battleground between rebel forces and the army for months.
Later on Tuesday, the UN General Assembly is due to meet, with much of its focus on the Syria crisis.
Russia can send its military personnel to help in the proposed operation to eliminate Syria’s chemical arms, Foreign Minister Sergei Lavrov says.
Mr Lavrov told Russian TV that military observers could help Syria destroy its stockpiles under a US-Russian deal.
He also accused the US of using “blackmail” over a UN resolution.
The international chemical weapons watchdog, the OPCW, says Syria has met the deadline to submit details of its estimated 1,000-tonne chemical arsenal.
This was the first step in a deal, brokered by Russia and the United States, to eliminate the weapons by the middle of next year.
US Secretary of State John Kerry has warned that not responding to the alleged use of chemical weapons by Syrian forces would be riskier than taking action.
He was speaking in London before returning to the US to urge Congress to back launching military strikes.
Russia has appealed to Washington to focus instead on peace talks.
Syria’s President Bashar al-Assad has said if the US does attack militarily, it should “expect every action”.
The US accuses Mr Assad’s forces of killing 1,429 people in a poison-gas attack on 21 August on the outskirts of the capital, Damascus.
Wrapping up a tour of European capitals, Mr Kerry said that if there was to be no response to the attack, then Damascus would think it could intimidate anybody.
William Hague says the UK and US remain “closely aligned” on Syria, after talks with his US counterpart John Kerry.
The UK foreign secretary said the two were working together to save lives and revive peace talks as well as press for a strong response to the Assad government’s use of chemical weapons.
Mr Kerry said the risks of doing nothing were greater than acting.
The two countries remained “true friends” despite the UK ruling out any military involvement, he insisted.
Their meeting in London comes as the US tries to gather support for military strikes.
UK Prime Minister David Cameron has said that Parliament’s vote last month means the UK will not join the US in any military action in response to Syria’s suspected use of chemical weapons.