Clashes raged in Syria Monday ahead of a UN deadline for the regime to pull its troops out of protest hubs, with the US saying Damascus has shown no sign of sticking to a plan to end the fighting.
Tensions also rose with Syria's neighbours after cross-border shootings killed a cameraman in Lebanon and wounded three people in Turkey.
Under a peace deal brokered by UN and Arab League envoy Kofi Annan, Syria's armed forces are supposed to withdraw from protest centres early on Tuesday, with a complete end to fighting 48 hours later.
But the truce plan already appears in jeopardy after Damascus said it would keep its side of the bargain only if rebels gave written guarantees they would also stop fighting.
At least 105 people were killed on Monday, the Syrian Observatory for Human Rights said after weekend violence claimed almost 180 lives, most of them civilians.
Monday's toll included 23 members of the security forces and eight rebel fighters, while the rest were civilians, the monitor said.
Washington said Syrian President Bashar al-Assad has shown no sign so far that his government is sticking by the peace plan.
"We certainly have seen no sign yet of the Assad regime abiding by its commitments," White House spokesman Jay Carney told reporters.
UN leader Ban Ki-moon made a final plea for Assad to stop attacks on civilians.
"The secretary general reiterates his demand that the government of Syria immediately cease all military actions against civilians and fulfill all of its commitments made through joint special envoy Kofi Annan," UN spokesman Martin Nesirky said.
The Britain-based Observatory said Syrian helicopters attacked the village of Kfar Zeita in Hama province as regular forces clashed with rebels.
At least 35 civilians were killed in regime bombardment of Latamna village in the province, the Observatory said.
"The regime had thought that it would control all areas (by April 10). As this is not happening, it is procrastinating to gain time," said Observatory chief Rami Abdel Rahman.
"If the Annan plan does not work, no other plan would, and Syria would plunge into a civil war."
On the northern border, shots fired from inside Syria wounded two Syrians and a Turkish translator in the first case of Syrian fire hitting people on Turkish soil.
State Department spokeswoman Victoria Nuland told reporters the United States was "absolutely outraged by today's report."
The incident -- on the eve of a visit by Annan to refugee camps -- prompted Turkey's foreign ministry to tell Syria's mission in Ankara to "immediately halt the shooting," a diplomatic source said.
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Some 25,000 Syrian refugees are currently in camps in Turkey's three provinces bordering Syria, after fleeing the deadly year-long crackdown.
Milliyet newspaper reported on Monday that Ankara would consider using troops to secure humanitarian corridors in border areas if refugee numbers rose above 50,000.
Lebanese Prime Minister Najib Mikati, whose government is dominated by pro-Syrian parties, condemned Monday's death of Lebanese television cameraman Ali Shaaban, who was killed inside Lebanese territory by Syrian gunfire.
Syria's SANA state news agency said the team from Al-Jadeed television came under fire as border guards opened fire in retaliation to an attack by "terrorist groups."
China urged Syria to honour its commitments.
"China urges the Syrian government and parties concerned in Syria to seize the important opportunities, to honour their commitment of ceasefire and withdrawal of troops," foreign ministry spokesman Liu Weimin said.
Syrian Foreign Minister Walid Muallem was due on Tuesday to meet Russian counterpart Sergei Lavrov in Moscow. Russia and Beijing blocked two UN Security Council draft resolutions condemning Damascus for its bloody crackdown.
On Sunday, the Syrian foreign ministry outlined the regime's new conditions.
"To say that Syria will pull back its forces from towns on April 10 is inaccurate, Kofi Annan having not yet presented written guarantees on the acceptance by armed terrorist groups of a halt to all violence," it said.
It said the regime was also awaiting written guarantees from the governments of Qatar, Saudi Arabia and Turkey "on stopping their funding to terrorist groups," referring to the regime's key regional critics.
Rebel army chief Colonel Asaad countered: "We are committed to the Annan plan... We will present our guarantees and our commitments to the international community, but not to this (Syrian) regime."
Free Syrian Army spokesman Colonel Kassem Saadeddine on Monday reiterated the FSA's readiness to cease fire on Tuesday "if the regime commits to respecting the terms of the (UN) plan."
After Turkey, Annan will travel to Syria's ally Iran, for a visit to Syrian refugee camps near the border, a Turkish diplomatic source said.
"I remind the Syrian government of the need for full implementation of its commitments and stress that the present escalation of violence is unacceptable," Annan said on Sunday.
The Security Council has formally endorsed the Tuesday deadline for a ceasefire, but Damascus said that the number of "terrorist acts" has risen since the deal was agreed.
The United Nations says more than 9,000 people have been killed since anti-regime protests broke out in March 2011, while monitors put the number at more than 10,000.
On Monday, Human Rights Watch accused Syrian security forces of executing more than 100 civilians and rebels in protest hubs since late 2011, urging any UN mission to Syria to collect evidence.