The UN-Arab League joint special envoy Kofi Annan said, upon arrival in the Syrian capital Damascus on Monday, that the carnage in central Syrian village of Houla which killed over 100 people was "appalling."

"In this crisis, I am personally shocked and horrified by the tragic incident in Houla," he said at the podium in the Dama-Rose Hotel in Damascus.

"This is an appalling crime and the Security Council has rightly condemned it," Annan said, adding that the UN has been requested by the Security Council to investigate the carnage in Houla.

Annan said the people who stand behind the incident should be held accountable, adding that Syria's ordinary citizens are paying the highest price in the 15-month conflict.

Annan urged the Syrian government to take "bold steps" to signal that it's in Syria's intention to resolve the crisis peacefully.

He also called "for everyone involved to help create the right context for a credible political process," making it clear that his message "is not only for the government but for everyone, every individual with a gun."

Annan said his six-point plan must be comprehensively implemented, "and this is not happening today."

The envoy said he expects to have "serious and frank" discussions with the Syrian President Bashar al-Assad, adding that he looks forward also to speak with a range of other people and actors during his three-day visit to Syria.