Syrian troops continued their crackdown on opposition forces on the eve of a visit by new U.N.-Arab League envoy Kofi Annan, who is calling for a political solution to the year-long crisis.

The Syrian Observatory for Human Rights said government soldiers stormed villages in the northwestern province of Idlib in an attempt to hunt down defectors belonging to the Free Syrian Army. Many there fear a major assault like the one that recently devastated the Homs neighborhood of Baba Amr.

Syrian opposition groups rejected calls by Annan to engage in dialogue with the government of President Bashar al-Assad.

Before his visit Saturday to Syria, the former U.N. chief warned against arming rebel forces, saying foreign intervention would make the situation worse. But opposition groups say a political solution is unrealistic as long as Mr. Assad is intent on using force against his opponents.

China's foreign ministry welcomed Annan's mission in Syria, saying it hoped the “impartial mediation” would result in peace talks. China also announced it will send an envoy to the Middle East and France next week to discuss the crisis.

China, along with Russia, has twice vetoed U.N. Security Council proposals that would have put pressure on Mr. Assad's government to end the conflict.

Russia on Friday reiterated its opposition to a new U.S.-backed proposal on the Syrian crisis. The Interfax news agency quoted Russian Deputy Foreign Minister Gennady Gatilov as saying the resolution was “unbalanced” because it did not hold both the government and rebel forces equally accountable for the violence.

Meanwhile, U.N. humanitarian chief Valerie Amos toured Syrian refugee camps along the Turkish-Syrian border on Friday before holding talks with officials in Ankara. At least 11,000 Syrians have sought refuge at the camps as government forces target rebellious areas along the border.

On Thursday, Amos told reporters in Damascus that the former rebel stronghold of Baba Amr has suffered “significant” devastation and that parts of the district were “completely destroyed” by the government assault. She briefly visited Baba Amr on Wednesday, the first foreign official to enter the area since the government ended a month-long assault last week.

The U.N. estimates that Syrian forces have killed well over 7,500 people since the anti-Assad uprising began a year ago. The government blames “terrorists” for the unrest, saying that 2,000 of its security forces have been killed in the conflict.