Syrian rights activists say government security forces backed by tanks have killed at least seven people in an assault on the central flashpoint city of Homs.

The activists said mobile phones, land lines and Internet services were cut off Wednesday in many parts of the city, which has been a hub for protests against President Bashar al-Assad. The raids come a day after activists said security forces killed two civilians, including a teenager, and another five bodies were found in the area.

Meanwhile, the Arab League's top diplomat has delayed a visit to Syria, which was due to begin Wednesday. Syria's state-run SANA news agency says the government asked Nabil Elaraby to postpone the trip “for objective reasons he was informed of” and that a new date will be given for the talks.

Elaraby has said he wants to express Arab concerns about the deadly violence that has rocked the country and listen to the opinions of Syrian leaders. In late August, Syrian authorities rejected an Arab League statement calling for an end to the bloodshed.

The European Union is moving to impose additional sanctions on Syria for the government's violent crackdown on dissent.

The French Foreign Ministry said Tuesday that diplomats are considering measures targeting companies that are linked to the repression of civilians in Syria. The new penalties could follow an EU oil embargo against Damascus that took effect Saturday.

United Nations Secretary-General Ban Ki-moon on Tuesday renewed calls for Mr. Assad to stop the crackdown and initiate reforms.

Also Tuesday, the U.S. ambassador to Syria, Robert Ford, said the Syrian government bears the responsibility for the violence, and that neither the protesters nor the international community believe the government is capable of “credible reforms that the Syrian people demand.”

His comments were posted on the Facebook page for the U.S. Embassy in Damascus. Ford also said the United States supports Syrians' rights to exercise the freedoms of speech and peaceful assembly.