UN and Arab League special envoy Kofi Annan arrived in Damascus for his scheduled meeting with Syrian President Bashar al-Assad.
Annan is expected to press the regime to end the crisis in the wake of the latest massacre of over a hundred people in Houla on 25 May.
"I urge the [Syrian] government to take bold steps to signal that it is serious in its intention to resolve this crisis peacefully, and for everyone involved to help create the right context for a credible political process," Annan said upon his arrival in Damascus.
"And this message of peace is not only for the government, but for everyone with a gun," he added.
The Assad regime has continued to blame Islamic militants for the massacre, which it termed a "terrorist act".
"The terrorist armed groups entered with the purpose of killing and the best proof of that is the killing by knives, which is the signature of terrorist groups who massacre according to the Islamist way," the Syrian government said in a letter published in state media outlets.
"Not a single tank entered the region and the Syrian army was in a state of self-defence. Anything other than this is pure lies," it said.
However, UN monitors who visited the area found artillery shells and fresh army tank tracks, though they could not determine who stabbed and shot the victims.
'We hid or played dead' - survivors
Several survivors of the Houla massacre told the BBC that they hid or played dead to survive the carnage.
Witnesses claimed that the army and the Shabiha militia, drawn from Assad's Alawite minority sect, were behind the gruesome killings, which the channel could not independently verify.
"We were in the house, they went in, the Shabiha and security, they went in with Kalashnikovs and automatic rifles," Rasha Abdul Razaq, one of the survivors, was quoted by the BBC as saying.
"They took us to a room and hit my father on the head with the back of a rifle and shot him straight in the chin," she said, adding that out of 20 people in the house, only four survived.
Another resident who took shelter in the attic to escape the attack said: "I opened the door and I saw bodies, I couldn't recognise my kids from my brothers. It was indescribable. I have three children, I lost three children".
International pressure mounts on Assad
World leaders have expressed their shock and dismay at the Houla massacre and called for renewed pressure on Assad to end the violence.
The UK, France and the US have started efforts to muster support to raise diplomatic pressure on Syria.
Foreign Secretary William Hague met his Russian counterpart Sergei Lavrov in Moscow, where he categorically denied any plans for a Libya-style military intervention in Syria, a major cause of Russian and Chinese opposition to any binding resolution on Syria. There were no signs of either Russia or China, Assad's two defenders, changing their stance.
French President Francois Hollande and Prime Minister David Cameron discussed Syria over the phone and condemned the brutality of the Assad regime.
The Friends of Syria plans to meet in France to discuss the crisis.
"The murderous folly of the Damascus regime represents a threat for regional security and its leaders will have to answer for their acts," Hollande's office said.
Russia and China backed a non-binding UN Security Council resolution which criticised the use of heavy weapons against civilians. They are of the opinion that both sides - Assad and opposition groups - should come together and work out an amicable solution to the crisis.
At least 10,000 people have lost their lives since the uprising against the Assad regime began in March 2011.