AMMAN (Reuters) - Syrian security forces shot dead at least 15 people on Friday after tens of thousands of protesters took to the streets demanding the overthrow of President Bashar al-Assad, witnesses and activists said. "Tell the world Bashar is without legitimacy," shouted several thousand protesters in the Damascus suburb of Irbin, the chants audible in a phone call to a witness at the protest. The Local Coordination Committees, a main activists' group, said it had the names of 14 civilians killed in the merchant city of Homs, the impoverished town of Kiswa south of Damascus and in the residential district of Barzeh in the capital. Another protester was shot dead in the town of Qusair, a rights group said. Syrian state television blamed the killings in Barzeh on armed men who authorities say are behind the violence in the three-month uprising, and said members of security forces were wounded. Syria has expelled most foreign journalists making it hard to verify witness accounts or official statements. "The security police first used teargas then they started shooting from rooftops when shouting against Assad continued," a Barzeh resident who gave his name as Hussam said by phone. "Three youths were killed and I saw two bodies shot in the head and the chest." In the central cities of Homs and Hama, protesters shouted "the people want the downfall of the regime," while in Deraa, cradle of the uprising, people waved banners rejecting Assad's promise in a speech this week to launch a national dialogue. Deraa protesters chanted slogans urging people in Damascus, which has seen fewer demonstrations than rural protest centres, to follow their lead. "People of Damascus, here in Deraa we toppled the regime," they chanted. Protests also erupted in western coastal cities and eastern provinces near Iraq. Syrian troops swept to the northern border with Turkey on Thursday, prompting another 1,500 refugees to flee across the frontier into camps which Turkish officials say now host more than 11,000 refugees. On Friday the European Union announced extended sanctions against Syria, including against three commanders of Iran's Revolutionary Guard accused of helping Damascus curb dissent. Syria denies Iran has played any role in tackling the unrest. Four Syrian officials were also targeted, bringing to 34 the number of individuals and entities on the list which already includes Assad and his top officials.