Emadeddin Al-Rachid, of the opposition National Salvation Congress, said Syrians would not repeat mistakes made in neighbouring Iraq, where fighting between Sunni and Shi'ite Muslims broke out after the fall of Saddam Hussein.

"Syria will not follow the path Iraq went down," Rachid told a news conference in Istanbul. "All Syrians are committed to the unity of the Syrian nation."

On Tuesday troops loyal to Assad killed 16 people in the Syrian city of Homs and rights group say more than 1,400 people have been killed since the unrest began in March.

"The regime is behind the sectarian clashes in Homs. They are distributing weapons to certain people to escalate sectarian tensions," Rachid said.

Gunmen, called shabbiha, from Assad's minority Alawite sect have been blamed for many of the attacks on civilians since demonstrators started taking to the streets in March to protest against the four-decade rule of Assad's family.

Fedaa Majouz, an organiser of the Congress, said the peaceful protests showed the Syrian people could work together rather than pursuing any ethnic or sectarian agenda.

"We will always work for unity in the Syrian nation, with its different sectarian (groups) and protect the identity, human rights and equal opportunities for all of them," Majouz said.

Alawites, a Muslim sect close to Shi'ism, are a minority in mostly Sunni Syria. Alawite officers hold leading positions in the mostly Sunni armed forces.

Alawites also receive preferential treatment in government and security jobs, but many Alawite villages are poor and some prominent Alawite figures lead part of the secular opposition.

Rachid and Majouz said the Syrian people were against any foreign military intervention.

The National Salvation Congress had planned two conferences on Saturday, one in Istanbul and one in Damascus to try to help align opposition inside and outside Syria. Only the Istanbul meeting was held after Assad launched a crackdown in Damascus.

Majouz said organisers of the external opposition were in contact with counterparts in Syria several times a day, and no stand was taken on any issue without coordinating with them.

The National Salvation Congress organisers would try to hold a conference in Syria soon and then the council would start appointing members to committees, such as fund-raising, media relations and promoting the opposition internationally.