UPDATE 1-Syria bombards major cities, weakening truce -activists

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* Army said it reserved right to respond to rebel attacks

BEIRUT Oct 27 (Reuters) - Opposition activists in Syria said forces loyal to President Bashar al-Assad had renewed their heavy bombardment of major cities on Saturday, further undermining a truce meant to mark the Muslim Eid al-Adha religious holiday.

The bombardment came on the second day of the truce called by international peace envoy Lakhdar Brahimi, who had hoped to use it to build broader momentum to end the 19-month-old conflict which has killed an estimated 32,000 people.

"The army began firing mortars at 7 a.m. I have counted 15 explosions in one hour and we already have two civilians killed," said Mohammed Doumany, an activist from the Damascus suburb of Douma, where pockets of rebels are based. "I can't see any difference from before the truce and now," he said.

Heavy machine gunfire and the sound of mortar bombs could be heard for the second consecutive day along the Turkey-Syria border near the Syrian town of Haram, a Reuters witness said.

Activists in the eastern city of Deir al-Zor and in Aleppo, where rebels control roughly half of Syria's most populous city, said that mortar bombs were being fired into residential areas.

Residents in Damascus aired footage of fighter jets which they said were bombing the suburbs of Erbin and Harasta.

The Syrian army said it had responded to attacks by insurgents on its positions on Friday, in line with its earlier announcement that it would cease military activity during the holiday while reserving the right to react to rebel actions.

A statement from the General Command of the Armed Forces detailed several ceasefire violations in which it said "terrorists" had fired on checkpoints and bombed a military police patrol in Aleppo.

More than 150 people were killed on Friday, said the Syrian Observatory for Human Rights, a British-based opposition organisation with a network of sources within Syria.

Most were shot by sniper fire or in clashes, the Observatory said, highlighting a temporary drop-off in the civil war's intensity in which Assad's forces have been conducting daily airstrikes and heavy artillery raids in most cities.

Forty-three soldiers were killed in ambushes and during clashes, it said, while state TV reported a powerful car bomb which had killed five people in Damascus.

TRUCE BREACHES

Violence had initially appeared to wane in some areas on Friday but truce breaches by both sides swiftly marred Syrians' hopes of celebrating Eid al-Adha, the climax of the Haj pilgrimage to Mecca, in peace.

Brahimi's ceasefire appeal had won widespread international support, including from Russia, China and Iran, President Assad's main foreign allies.

But there are few signs that either side in the conflict has respected the truce. A Reuters cameraman in the Turkish border village of Besaslan in southern Hatay province said he could hear the sound of a helicopter circling on the Syrian side of the border.

Turkish ambulances were ferrying wounded people from an unofficial border crossing for treatment in Turkey.

The war in Syria pits mainly Sunni Muslim rebels against Assad, who is from the minority Alawite sect which is distantly related to Shi'ite Islam. Brahimi has warned that the conflict could suck in Sunni and Shi'ite powers across the Middle East.

Brahimi's predecessor, former U.N.

chief Kofi Annan, declared a ceasefire in Syria on April 12, but it soon fell flat, along with the rest of his six-point peace plan.

Divided international powers have been unable to stop the violence with the West condemning Assad but blaming Russia, Iran and China for supporting Damascus.

Russia's deputy foreign minister Gennady Gatilov tweeted on Saturday that "Westerners" in the United Nations Security Council had prevented the body from condemning a bomb attack in Damascus on Friday, which the Syrian government blames on rebels it labels as "terrorists."

"(The Syria opposition's) course for continuation of violence is self-evident," Gatilov said.

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