DAMASCUS: Violence in Syria continued for the fourth straight day to chip away at what remains from a ceasefire that has effectively collapsed, leaving at least 28 people dead on Monday in reciprocal shellings between government forces and opposition in the country`s largest city while a bomb blast disrupted a relative quiet in a Damascus suburb that is home to one of the Shia shrineshere.

At least 20 people were killed in the shelling on Aleppo, pro-government media and activist-run monitoring groups said; while eight died when a suicide bomber detonated his explosive-packed vehicle at a military checkpoint in the Damascus suburb of Sayyida Zeinab.

In the past week, nearly 150 people have been killed in northern Syria and near Damascus, marking a major escalation that has seen a fragile truce take a downward spiral to levels of violence unseen since the Feb 27 ceasefire, engineered by the US and Russia, took hold.

The ceasefire doesn`t include the militant Islamic State (IS) group and its rival Al Qaeda branch in Syria, the Nusra Front.

The IS claimed responsibility forthe suicide bombing.

The Aamag news agency, linked to the extremist group, said fighters detonated an explosives-packed vehicle at a gathering of government troops in the suburb of Sayyida Zeinab.

The Syrian pro-government Al-Ikhbariya TV station showed footage of a slight depression on a road near a checkpoint where the bomb was said to have gone of f. The wreckage had already been removed.

Al-Manar TV, run by the Hezbollah militant group, said eight people were killed in the blast. The Shia militants have aheavy presence in the suburb. The Syrian Observatory for Human Rights, an activist-run monitoring group, gave the same toll.

Syrian state TV said seven people were killed and 20 wounded.

The heavily guarded shrine to Sayyida Zeinab receives thousands of pilgrims each year.

Allies of the embattled Damascus government have mobilised Shia fighters from Iran, Iraq and Lebanon to fight on the side of President Bashar Assad`s forces on the grounds of defending the shrine and preserving the country`s religious plurality.

A previous bombing in theSayyida Zeinab suburb, claimed by the IS group, killed some 130 people in February.

Meanwhile, violence raged for the fourth straight day in Syria`s largest city, the deeply contested Aleppo.

The government news agency said rebel shelling of governmentheldneighbourhoods left16 people dead.

The Observatory put the number at 19, including three children. The group said 120 people were injured.

Also, government shelling of rebelheld areas in the city left at least 3 killed, including a 6-year old girl.

The Observatory said four were killed in the government shelling on the al-Jazamati neighbourhood. Aleppo, Syria`s largest city and onetime commercial centre, has been bitterly contested since 2012.

Opposition groups control the eastern part of the city but have been boxed-in by government forces, and are now linked to the surrounding area by a single narrow corridor to the northwest.

The government and its opponents exchanged blame for violations thathave left over 70 people dead in Aleppo alone since Friday.-AP