Devastating air raids by Syrian government forces using 'barrel bombs' leaves 45 dead including 12 children Bombs are wildly-inaccurate crude devices filled with explosives and fuel Often land near schools and markets, causing massive damage on impact One strike hits Aleppo, while another is on Turkish border town of Azaz Estimated 15 dead in Azaz strike and at least 30 more in Aleppo attacks William Hague: 'I am deeply concerned at the escalating level of violence' Some 45 people were killed yesterday - including at least 12 children - as government forces widened a bombing campaign in rebel-held areas of Syria, activists said. One strike hit Syria's largest city of Aleppo, while another on the Turkish border town of Azaz was claimed to be the latest attack using powerful-but-inaccurate "barrel bombs" on the northern region. The Azaz attack suggests the Government is expanding its targets a week after it began a heavy air offensive against Aleppo on December 15, dropping the bombs on rebel-held areas from helicopters. 'Barrel bomb' raids: Strikes on the Aleppo areas of Sukkari, Maadi, Marjeh and Nairab left at least 30 dead Warzone: People are rescued from buildings after Syrian army helicopters dropped 'barrel bombs' on Aleppo Emergency: Some 45 people were killed as government forces widened a bombing campaign in northern Syria Taken away: A concerned man holds a child as people are rescued from buildings after the strikes on Aleppo Activists said 15 people were killed in the Azaz strike, while it was reported that air raids on the Aleppo areas of Sukkari, Maadi, Marjeh and Nairab left at least 30 people including 12 children dead. The Britain-based Syrian Observatory for Human Rights said the death toll could rise. On Sunday, 65 were killed near an Aleppo marketplace in one of the air campaign's bloodiest days, activists said. Rami Abdurrahman from the Observatory said that air raids on Aleppo have killed at least 301 people including 87 children, 30 women and nearly 30 opposition fighters since mid-December. But that figure did not include those reported killed yesterday. The aid group Doctors Without Borders has said the bombs killed at least 189 people and wounded 879 in the first four days alone. Concern: The Britain-based Syrian Observatory for Human Rights said the death toll from the strikes could rise Highly dangerous: Barrel bombs are crude devices filled with explosives and fuel that are wildly inaccurate Saved: The barrel bombs often land near schools and market places, causing massive damage on impact Climbing out: The Syrian Government has not commented on the use of the crude weapons in attacks Claim: Syrian President Bashar Assad says his army is fighting 'terrorists' backed by foreign states British Foreign Secretary William Hague said: "I am deeply concerned at the escalating level of violence in Syria. I am deeply concerned at the escalating level of violence in Syria Foreign Secretary William Hague I condemn the use of brutal and indiscriminate weapons in densely-populated civilian areas, such as we have seen in Aleppo in recent days. The main Western-backed Syrian opposition group, the Syrian National Coalition, warned that if the bombing campaign against Aleppo continues it will not take part in UN-sponsored peace talks. The group's Secretary General Badr Jamous was quoted in a coalition statement as saying they will boycott the talks planned for January 22 in Switzerland if the air raids do not stop. Helping hand: People are rescued from buildings after Syrian army helicopters dropped 'barrel bombs' Shocking data: Air raids on Aleppo have killed at least 301 people including 87 children since mid-December Saved: A trapped person is rescued from a building after 'barrel bombs' were dropped yesterday in Aleppo Fears: Foreign Secretary William Hague said he was 'deeply concerned at the escalating level of violence in Syria' Barrel bombs are crude devices filled with explosives and fuel that are wildly inaccurate - often landing near schools and market places, causing massive damage on impact. The Government has not commented on the use of the crude weapons, nor on the intensified strikes over Aleppo. But the timing suggests that President Bashar Assad could be trying to strengthen his position a month ahead of planned peace talks in Switzerland. In the capital Damascus, President Assad received an Australian delegation telling them his government is fighting extremists who might strike anywhere in the world, the state media said. Stretcher: The main Western-backed Syrian opposition group, the Syrian National Coalition, warned that if the bombing campaign against Aleppo continues it will not take part in UN-sponsored peace talks Difficult conditions: A figure can hardly be seen through the dust as people are rescued following the bombing Rescuers: The timing suggests that President Assad could be trying to strengthen his position a month ahead of planned peace talks in Switzerland Teamwork: Rescuers stand by as people are helped out of a building following the bombing raid in Syria The Syrian Arab News Agency said the delegation included academics, researchers and activists. "What is happening in Syria and the region in general affects the whole world," SANA quoted Assad as telling the delegation. The country is facing fanatic takfiri ideology that has no borders. It is an epidemic that could strike anytime and anywhere. The term "takfiri" is usually applied to hard-liners who consider other Muslims to be infidels. President Assad said in the past that fighters from more than 80 countries have come to Syria to fight against his forces. He says his army is fighting "terrorists" backed by foreign states.