By Mariam Karouny

BEIRUT (Reuters) - Syrian forces killed at least eight people when they opened fire to disperse protests against President Bashar al-Assad after Friday prayers in Damascus and Homs, activists said.

Rami Abdel-Rahman, head of the British-based Syrian Observatory for Human Rights, said three died in the Damascus suburb of Douma, one in Zabadani near the Lebanese border and four in Bab Sbaa, a district in the central city of Homs. He said at least 25 people were wounded.

Activists said protesters also came under fire in the tribal region of Deir al-Zor on the border with Iraq and in the city of Hama.

Video footage showed protesters holding banners urging the international community to protect civilians.

Some chanted "Syria, Assad is a germ here" and "We do not love you (Assad). Leave, you and your party."

An activist told Al Jazeera television that protesters had burned the flags of Russia and China for blocking a European-drafted U.N. Security Council resolution urging Syria to end its six-month crackdown on protesters.

Russian President Dmitry Medvedev said on Friday the Syrian leadership should quit power if it could not carry out promised reforms, the state-run Russian news agency RIA reported.

"We are using our channels and are actively working with the Syrian leadership. We are demanding that the Syrian leadership implement the necessary reforms," Medvedev said.

"If the Syrian leadership is incapable of conducting such reforms, it will have to go, but this decision should be taken not in NATO or certain European countries. It should be taken by the Syrian people and the Syrian leadership."

The remarks were Medvedev's bluntest warning yet to Assad, whose country has close ties with Moscow, one of its main arms suppliers, and hosts a Russian naval maintenance facility.

RED LINE

Russia has warned it will oppose almost any U.N. resolution condemning Assad. It refrained from using its Security Council veto in March to obstruct NATO air strikes in Libya, but Syria appears to be a red line for Moscow.

While Assad has sent troops and tanks to crush protests, he has also promised reforms. He has ended a state of emergency and given citizenship to tens of thousands of Syrian Kurds. He has also promised a parliamentary election in February.

Many of Assad's opponents say his reform promises are hollow and that his government has forfeited all legitimacy after killing at least 2,900 civilians, by a U.N. count.

Syria accuses foreign powers of arming demonstrators and blames violence on armed groups. Deputy Foreign Minister Faisal Mekdad told the U.N. Human Rights Council on Friday that more than 1,100 security personnel had been killed in the unrest.

"I would like to assure the international community that those who committed violations of human rights will be held to account," he told reporters in Geneva. He denied allegations loyalist forces shot soldiers refusing to fire on protesters.

Riad al-As'aad, the most senior officer to defect from Syria's armed forces, said there was no option but to topple Assad by force.

As'aad, now living under Turkish government protection in Hatay province on the Syrian border, said some 15,000 soldiers, including officers, had already deserted, and he was waiting to move his command inside Syria.

(Reporting by Mariam Karouny; editing by Andrew Roche)