Five UAE nationals have been killed in a bomb attack at a guest house in Afghanistan's Kandahar on Tuesday, which left at least 13 people dead and 17 others injured. <br/><br/>The men were carrying out humanitarian, educational and development projects in Afghanistan, official news agency of UAE reported.The UAE's ambassador to Afghanistan, Juma Mohammed Abdullah al-Kaabi, was also injured in the attack.<br/><br/>UAE President Sheikh Khalifa bin Zayed Al Nahyan mourned the death of the men and directed all ministries, government departments and institutions across the country to fly the flag at half-mast for three days.<br/><br/> "There is no human or moral or religious justification for the bombing and killing of people carrying out humanitarian work," said UAE Vice President and Prime Minister Sheikh Mohammed bin Rashid Al Maktoum.<br/><br/>The attack has been strongly condemned by the Gulf Cooperation Council, with the GCC secretary-general Abdullatif Al Zayani calling it a "cowardly, terrorist act which violates human and ethical values and principles."