A suspected chemical attack killed at least 58 civilians including several children in rebel-held northwestern Syria on Tuesday, a monitor said, with the opposition accusing the government and demanding a UN investigation, reports AFP from Khan Sheikun in Syria.
The attack in the town of Khan Sheikhun left dozens suffering respiratory problems and symptoms including vomiting, fainting and foaming at the mouth, the Britain-based Syrian Observatory for Human Rights said. A hospital in the town where doctors were treating victims of the attack was also bombarded, an AFP correspondent said. The entrance of the building was hit, bringing down rubble on top of medics who had earlier been seen dousing a steady stream of arrivals to wash away chemical residue.
The violence came as the European Union and UN hosted a conference in Brussels on Syria's future, with confusion over Washington's position on the issue of Syrian President Bashar al-Assad's future.
The Observatory said the attack on a residential part of Khan Sheikhun came in the early hours of Tuesday, when a warplane carried out strikes that released "toxic gas".
It said 11 children were among the dead, with at least 160 injured, and that many people were dying even after arriving at medical facilities.
The monitor could not confirm the nature of the gas or whether the strikes were carried out by Syrian warplanes or those of government ally Russia.
It relies on a network of sources inside Syria and says it determines whose planes carry out raids according to type, location, flight patterns and munitions used.
An AFP journalist in Khan Sheikun saw a young girl, a woman and two elderly people dead at the hospital prior to the bombardment, all with foam still visible around their mouths.
Doctors at the facility had been using basic equipment, some not even wearing lab coats, and attempting to revive patients who were not breathing.
The town is in Syria's Idlib province, which is largely controlled by an alliance of rebels including former Al-Qaeda affiliate Fateh al-Sham Front.
The province is regularly targeted in strikes by the regime, as well as Russian warplanes, and has also been hit by the US-led coalition fighting the Islamic State group, usually targeting jihadists.
Syria's leading opposition group, the National Coalition, accused the "regime of the criminal Bashar" of being behind the attack.
It called on the UN Security Council to convene an emergency session, "open an immediate investigation and take the necessary measures to ensure the officials, perpetrators and supporters are held accountable."
"Failure to do so will be understood as a message of blessing to the regime for its actions," the statement added.
Syria's government officially joined the Chemical Weapons Convention and turned over

its chemical arsenal in 2013, as part of a deal to avert US military action. But there have been repeated allegations of chemical weapons use by the government since then, with a UN-led investigation pointing the finger at the regime for at least three chlorine attacks in 2014 and 2015.
Meanwhile, the White House accused Bashar al-Assad of carrying out a "reprehensible" and "intolerable" chemical attack in Syria yesterday, the sharpest criticism of his regime since Donald Trump became president.  Press secretary Sean Spicer said an "extremely alarmed" Trump was briefed extensively by security aides on the suspected attack, which killed dozens in the rebel town of Khan Sheikhun.
"Today's ( Tuesday) chemical attack in Syria against innocent people, including women and children, is reprehensible," Spicer said in a prepared statement.
The administration, Spicer said, was "confident" that Assad was to blame but refused to speculate on how the US would respond.
"I'm not ready to talk about our next step, but we will get there soon," he said. The Syrian army and Russia have categorically denied involvement.
"Any leader who treats their people with this kind of activity, death and destruction. Yeah. I don't think anyone would wish this upon anybody." The United Nations Security Council is scheduled to meet Wednesday to discuss the attack on Khan Sheikhun.