DAMASCUS - Remorseless violence reported across Syria have practically unravelled a UN-backed cease-fire deal, with government forces and armed groups blaming each other for the incessant fighting, now in its 19th month.

Armed groups on Sunday opened fire on army checkpoints in the eastern province of Deir al-Zour, violating the truce for the third straight day, according to Syria's state-run SANA news agency.

Government troops have fought back and killed three "terrorists" including a leading figure linked to an al-Qaida terror network, the news agency said.

Meanwhile, the Local Coordination Committees, an activists' network, reported airstrikes and strafing carried out by the Syrian troops on rebel strongholds near the capital Damascus and on al-Mayadden area in the eastern Deir al-Zour province.

There has been no independent confirmation on the activists' account.

With the conflicting parties blaming each other, a workable cease-fire proposed by international peace envoy Lakhdar Brahimi has faded away.

Brahimi has been shuttling among regional countries to push for the truce during the four-day Muslim Eid al-Adha holiday as a prelude for further pacification. The violence, however, continued unabatedly.

The Syrian government has accused "terrorist groups" of breaking the truce, vowing to crush them with an iron fist and root them out of the country.

In a statement carried by SANA on Sunday, the government recounted the armed rebels' alleged violations to the cease-fire truce for the third straight day.

It said armed groups blasted earlier on Sunday an oil pipeline in Deir al-Zour, among many other attacks on checkpoints over the past 24 hours.

"These terrorist groups must be confronted, their remnants chased and an iron fist used to exterminate them and save the homeland from their evil," the statement said.

In another development, the Britain-based Syrian Observatory for Human Rights, an activists' network, said that armed rebels in Syria released on Sunday 120 Syrian Kurds, who were snatched by the armed groups in northern Syria.

The latest incident indicates to what extent the Syrian Kurds have become involved in the fighting against the armed rebels, mostly in some Kurds-dominated northern parts of Syria.

Meanwhile, Syria's state TV on Sunday denied as "totally untrue" reports by the Saudi-funded al-Arabyia TV that the armed rebels in the northern province of Aleppo have taken control over a headquarters of Syrian air force intelligence.

The Syrian network also denied another al-Arabyia report that a booby-trapped car ripped through the police academy in the capital Damascus on Sunday.

Since the country's crisis began 19 months ago, more than 20,000 people, mostly civilians, have reportedly died in Syria. Up to 2.5 million Syrians urgently need humanitarian aid, and over 340,000 have fled to Syria's neighboring countries -- Lebanon, Jordan, Turkey and Iraq, according to UN estimates.