Syrian troops defied a UN peace deal Tuesday with new attacks on rebel-controlled areas, but the man who brokered the ceasefire said a truce can still be reached.

Despite shelling and gunfire in opposition strongholds across Syria, UN and Arab League's joint special envoy Kofi Annan said his peace plan is "very much alive."

"If you want to take (the plan) off the table, what will you replace it with?" Annan told reporters in Hatay, Turkey, where he visited a refugee camp for Syrians fleeing their country.

"We still have time between now and the 12th (Thursday) to stop violence," Annan said, suggesting the matter would be raised at the Security Council later in the day.

In the meantime, he said, "I appeal to all, the government in the first place," to halt fighting without further conditions.

Under the terms of the peace agreement, Syrian troops were meant to be out of major towns and villages Tuesday morning, with a complete cessation of hostilities by early Thursday.

But according to activist groups in Syria and abroad, who estimate as many as 1,000 people have been killed in the week leading up to this latest deadline, there have been no signs of large-scale withdrawals.

Annan's appeal came hours after Syria's Foreign Minister Walid Moallem, who is currently visiting Moscow, said that the troop pullback had in fact begun.

Annan's insistence that President Bashar Assad still has time to meet the peace plan requirements was echoed by Syria's Ambassador to Canada, Bashar Akbik, on CTV's Power Play Tuesday.

"No, we can't say (the ceasefire) has failed. It's too early," Akbik said. "The plan doesn't say that on the 10th of April the Syrian army will withdraw from all cities. They will start withdrawing from different areas in a tangible way…and we are trying to do this."

Akbik also said Moallem is in active discussions with his Russian counterpart on how to implement Annan's plan.

For his part, Russian Foreign Minister Sergey Lavrov told reporters that Syria "could have been more active and decisive" in implementing the ceasefire.

Canadian Foreign Minister John Baird, a vocal critic of the Assad regime, told Power Play that Ottawa is "just horrified" at the escalating violence in Syria and the growing humanitarian crisis.

Asked whether Syrian diplomats in Canada should be sent home in light of stalled peace talks, Baird said that may be discussed in the future but the focus should be on "working constructively" to resolve the crisis.

Akbik said Syrian delegates are "isolated" in Ottawa and he criticized Baird for "inciting our people against the government" with his bold statements against the regime.

Meanwhile, witnesses to the bloodshed in Syria described attacks across the country Tuesday, including in the northwest town of Mariah.

Sami Ibrahim of the Syrian Network for Human Rights claimed helicopters took part in attacks that injured 100 people.

Speaking to CTV's Canada AM, Ibrahim insisted, "Nothing has been changed."

In fact, Ibrahim said, his sources counted 15 dead in a barrage of up to 100 rockets on several neighbourhoods in the city of Homs Tuesday. He also said attacks had been reported in Idlib, and there were accounts of troops loyal to Assad carrying out arrests in the Harasta suburb of Damascus.

The conflict is further threatening to spill over Syria's borders, after attacks crossed into neighbouring Turkey and Lebanon on Monday.

After visiting the refugee camp where witnesses said two people were killed by cross-border gunfire from Syrian troops, Turkish Prime Minister Recep Tayyip Erdogan said Tuesday his country is weighing a response that could include measures "we don't want to think about."

He did not elaborate.

Annan's plan is widely seen as a last chance to end the violence that's marked a 13-month uprising against Assad's regime. So far, the United Nations estimates 9,000 people have been killed in the crisis.

Already-low expectations for the peace plan's implementation took a further beating on Sunday, when Assad issued a demand the opposition guarantee, in writing, they will relinquish their weapons.

In response, the opposition said it would honour the terms of the UN-backed truce, but would not issue guarantees to a regime it does not recognize.

Akbik claimed there are 33 armed factions in Syria, and that only two of them are affiliated with the main opposition, the Free Syrian Army.

He said Syria has asked Annan to make contact with those armed groups and the countries supplying them with money and guns, "but we received no response."

"If we withdraw the army from a certain area, how can we guarantee that the gunmen won't come back and impose their control on these areas?" Akbik said.

Until they backed this latest peace plan, Russia and China had both used their Security Council sway to blocked any UN condemnation of Assad.

But with that hurdle cleared, there has been no suggestion the international community is considering military intervention.

The rhetoric continues, however, with French Foreign Ministry spokesperson Bernard Valero on Tuesday dismissing Syria's claims of a withdrawal as "a new expression of this flagrant and unacceptable lie."

British Foreign Secretary William Hague also accused Assad's regime of exploiting the deadline "as a cover for intensified military efforts to crush Syria's opposition."

With files from The Associated Press