DAMASCUS (AFP) - Syrian forces on Saturday stormed villages in the northwest and rounded up civilians in the flashpoint city of Homs, activists said, as UN officials pointed to possible crimes against humanity in the crackdown on dissent. Activists charged that the authorities were stepping up their repression of four months of protests against the regime of President Bashar al-Assad ahead of the start on August 1 of the holy fasting month of Ramadan. In a statement released on Friday after another day of bloody unrest, with eight protesters were killed by security forces, UN officials said crimes against humanity may have been committed in Syria. The concerns were expressed in a joint statement by Francis Deng, special adviser to Secretary General Ban Ki-moon on the prevention of genocide, and Edward Luck, special adviser on the responsibility to protect. "Based on available information, the special advisers consider that the scale and gravity of the violations indicate a serious possibility that crimes against humanity may have been committed and continue to be committed in Syria," they said. They urged an "independent, thorough, and objective investigation" of the events in Syria and echoed calls by Ban to Assad's government to allow humanitarian access to areas affected by the unrest. The London-based Syrian Observatory for Human Rights says 1,483 civilians have been killed since protests erupted March 15 in the autocratic Arab country. Rights group say more than 12,000 people have been arrested and thousands fled the country, many to Turkey and Lebanon.