NEW : Violence erupts in the Syrian city of Aleppo . U.S. Ambassador was among those visiting northern Syria . Many had lost family members , who they said were either killed , missing or in hiding . A human rights official says hundreds of peaceful protesters are arrested in Aleppo . More than 10,000 Syrian refugees reportedly have crossed the border into Turkey .
NEW : Violence erupts in the Syrian city of Aleppo . U.S. Ambassador was among those visiting northern Syria . A human rights official says hundreds of peaceful protesters are arrested in Aleppo . More than 10,000 Syrian refugees reportedly have crossed the border into Turkey .