Russia has said the crisis in Syria resembles "a civil war".
President Bashar al-Assad's government forces are engaged in an increasingly violent struggle with protesters and rebel fighters which began in March and has since killed thousands of people.
Foreign Minister Sergei Lavrov called for both sides to end the bloodshed one day after an attack by rebel soldiers on a military base near to the capital Damascus.
"We see television reports that say some new force, the so-called Free Syrian Army, I believe, organised an attack on... a building belonging to the Syrian armed forces," he said, according to Reuters.
"This is already completely similar to real civil war."
The attack on the base by the Free Syrian Army (FSA), an increasingly powerful group of defected army officers, was seen as the boldest so far on the regime.
FSA commander Col Riad al-Asad told the BBC that using force was a last resort, but said that "it is our right to defend our people because the international community does nothing".
The apparent growing strength of the FSA should be a concern for those who wanted to see an end to violence, Russia's foreign minister said.
In an apparently co-ordinated move, China also issued a statement which said it was "highly concerned" by the attacks.
"We hope that all relevant parties will work together to accelerate the implementation of the resolution scheme reached between the Arab League and Syria and seek to resolve the Syrian crisis through political means," foreign ministry spokesman Liu Weimin said.
Russia and China both vetoed a recent United Nations resolution that condemned President Bashsar al-Assad's regime for a violent crackdown on protesters which according to the UN has killed 3,500 people.
Russia has traditionally been a strong ally of Syria. It is one of the regime's biggest suppliers of arms and the country also hosts a Russian naval maintenance facility.
Meanwhile Turkey, which has led the international criticism of the Assad regime, said that not enough was being done by other countries to bring an end to the violence.
Earlier, the Arab League said it would maintain Syria's suspension from the organisation, and said the government had three days to its its "bloody repression" of the protests.
The 22-member League added that Assad's regime must allow international monitors into the country and pull its tank out of civilian areas else it would face sanctions.