Any hope of salvaging the short-lived ceasefire in Syria has been well and truly dashed over the weekend after the city of Aleppo became the focal point for international concern. Here's a quick guide to what's going on:
What's happening in Syria now?
Syria's five-year long civil war was reignited with a vengeance last week after a brief cessation of hostilities ended. After a one-week ceasefire, the Syrian regime under President Bashar al Assad began a new offensive against rebel groups in and around the northern city of Aleppo.
The ceasefire agreement between the government and rebel forces, who want Assad removed from power, officially came to an end last Monday afternoon despite efforts by the U.S. and Russia, an ally of the Syrian regime, to rescue it.
Instead, Russia has joined Syria in an escalation of airstrikes against rebel-held areas in Aleppo. Thousands of civilians are trapped in the city and the U.K.-based Syrian Observatory of Human Rights and United Nations have warned that the death toll is rising due to the airstrikes.
Why did the ceasefire fail?
The Syrian civil war is complicated by the involvement of other players, including western coalition forces trying to combat the advance of terrorist group the so-called Islamic State.
As well as prominent rebel groups in Syria, there are a multitude of smaller, disparate opposition groups (all are viewed as "terrorists" by the Syrian regime), making a ceasefire hard to maintain and control.
In the short time it was in operation, both the Syrian regime and rebel groups accused each other of multiple violations of the ceasefire before it finally fell apart last Monday. Extra pressure was also put on the agreement after U.S.-led coalition airstrikes killed dozens of Syrian soldiers when they believed they were targeting ISIS positions.
Russia accused the U.S. of deliberately undermining the ceasefire but Russia and Syria were also accused of carrying out an attack on an aid convoy and sabotaging the agreement. Trust between Russia and the U.S. has hit a new low as a result.
What's at stake?
The ceasefire was seen as a way to allow vital humanitarian aid through to thousands of Syrian civilians caught up in the fighting.
The UN says the attacks on Aleppo have left nearly two million people without water and some 275,000 people are believed to be trapped in the rebel-held eastern area of the city alone. The exact death toll as it stands is uncertain with many people believed to be trapped under destroyed buildings.
The Syrian Observatory for Human Rights said on Saturday that 52 people including women and children had been killed in eastern Aleppo so far in the offensive but the UN said this weekend that airstrikes were reported to have killed 213 people in Aleppo province, 139 of them in eastern Aleppo.
Western powers are united in their disapproval of Russia and Syria's bombing campaign and have demanded an end to the offensive, saying that both countries were committing war crimes.
At an emergency summit of the UN Security Council on Sunday, the British, U.S. and French envoys walked out of meeting when Syria's ambassador was called to speak, signaling their anger.
The British Ambassador to the UN, Matthew Rycroft, summed up his criticism, telling the council that "after five years of conflict, you might think that the (Syrian) regime has had its fill of barbarity – that its sick bloodlust against its own people has finally run its course….But this weekend, the regime and Russia have instead plunged to new depths and unleashed a new hell on Aleppo."
What happens next?
Relations between the west, Russia and Syria could not be worse and all sides recognize that re-establishing a peace deal is a long way off.
Even Russia's Ambassador to the UN, Vitaly Churkin, said on Sunday that bringing peace to Syria was "almost an impossible task now" and again accused opposition groups of sabotaging the ceasefire.
At the Security Council meeting there were renewed appeals from the UN Special Envoy for Syria, Staffan de Mistura, for Russia and U.S. to cooperate in order to to pull Syria "away from the brink."
In an UN Security Council statement, Mistura said that the Council "has the responsibility to relaunch the cessation of hostilities."
He reiterated his appeal for a common course of action, led by Russia and the UN, in three areas: "ensuring a ceasefire; establishing weekly 48 hour pauses in the fighting to allow in aid and repairs for Aleppo's damaged water and power facilities; and allow medical evacuations for urgent cases in and around the city."