At least 65 civilians have been killed by air strikes in Yemen's Taiz, including 17 people from one family, Doctors Without Borders (MSF) reported. The deaths occurred when Saudi-led Arab coalition air strikes hit civilian homes, MSF said in a statement released on Friday. During the past three days, Houthi rebels have reportedly been heavily shelling residential neighbourhoods in Taiz, the country's third city. At least 28 civilians, including 13 children were killed in these attacks. According to medical sources and the MSF, the Saudi-led coalition retaliated by targeting Houthi positions and unintentionally ended up hitting residential areas in Taiz. "We understand that during this most recent air strike, 17 houses were hit and more than 65 people are believed to have died, among them at least 17 children and 20 women," MSF reported. "Twenty-three people were injured and were brought to one of the MSF supported hospitals which are partially functioning." Many others are believed to have been injured or killed in the past week due to air strikes on densely populated areas. Al Jazeera's Hamdi al-Bakari, reporting from Yemen, said at least 33 Houthi fighters were killed in the air strikes and during fighting, while 40 others were injured. Out of the 20 hospitals in Taiz, MSF said only seven hospitals still receive the wounded. Since March, MSF-supported hospitals in Taiz have treated more than 4 300 patients.Children casualtiesreport released on Thursday by UNICEF says that 398 children have been killed and 377 others have been recruited to fight since the Saudi-led coalition began air strikes in Yemen. An average of eight children are being killed or maimed everyday, UNICEF reported. "Across the country, nearly 10 million children - 80 percent of the country’s under-18 population - are in need of urgent humanitarian assistance. More than 1.3 million people have been forced to flee their homes," the report stated. Overall, the UN human rights office said on Tuesday, at least 1 950 civilians have been killed in the fighting and 1.3 million others have fled their homes. Coalition helicopter crash In another development, a helicopter from the Saudi-led coalition crashed along the Saudi border, killing two pilots, according to the Saudi Press Agency. In a statement, the Joint Forces Command said that the two pilots were killed when their Apache helicopter crashed, while attacking Houthi rebels on the southern boundary of Jazan. The Joint Forces Command said an investigation was under way, to uncover the causes of the accident.