Syrian government troops reportedly shelled three dissident provinces on Wednesday, a day after Damascus pledged to observe an international plan to end the violence, dpa reported.
Government forces attacked the provinces of Idlib, Homs and Daraa, according to activists. The areas have figured prominently in the revolt that started more than a year ago against the rule of president Bashar al-Assad.
At least 21 people, including government soldiers and rebels, were killed in Wednesday's violence, the activists added.
Syria tops the agenda of an Arab League summit due to take place in Iraq on Thursday.
A draft communique to be debated by Arab leaders at the summit - from which Damascus is excluded - calls on the Syrian government and opposition to engage in a "serious national dialogue." The draft also rejects military intervention in the country, regional media reported Wednesday.
But Syria was quick to announce that it would reject "any initiative" from the Iraq summit.
"Damascus will not deal with any initiative" launched by the summit, official Syrian television reported, quoting a statement by Foreign Ministry spokesman Jihad Makdissi.
On Tuesday, Syria accepted a peace plan proposed by the United Nations-Arab League envoy Kofi Annan to end the conflict, which the UN says has left more than 9,000 dead since it started in March 2011.
The plan, which has been endorsed by the UN Security Council, calls for a full ceasefire to be supervised by UN monitors, humanitarian access and inclusive talks between the Syrian government and opposition.
On Wednesday China urged Syria, its main ally in the region, to respect its commitments under Annan's plan.
In recent days, the former UN chief has held talks in China and Russia to seek support for his mediation efforts. The countries had previously vetoed two UN Security Council resolutions against Syria.
"We are happy to see the Syrian government has accepted the six-point proposal of special envoy Annan, and believe it will be conducive to the political settlement of the Syrian issue," said Chinese Foreign Ministry spokesperson Hong Lei.
Three Syrian government soldiers were killed Wednesday when regular army forces tried to enter the central town of Al-Rastan, currently controlled by army defectors, reported the opposition Syrian Observatory for Human Rights.
Activists said that seven rebels were also killed in the Al-Rastan clashes, in which 16 government soldiers were injured.
In Hama, another volatile province, government forces backed by tanks stormed an historic town after a two-week siege in their hunt for rebels, killing seven, activists in the area told dpa.
"Tanks are rumbling into the town of Qalaat al-Madeek after rebels made a retreat," Firas al-Hamawi said via satellite phone.
Clashes were also reported between rebels and government forces in Daraa near the border with Jordan, killing four people including a Syrian army officer, opposition activists reported.
News from Syria is hard to verify as the government bars most foreign media from the restive areas.
Meanwhile, more than 1,000 Syrian refugees flooded into Jordan in a 12-hour period Wednesday, arriving illegally from the cities of Homs and Hama, according to humanitarian and security sources.
A Jordanian security source confirmed the exodus and said the refugees were transferred to a fortified compound in the border city of Ramtha, some 90 kilometres north of Amman, to undergo security background checks.
In eastern Lebanon, soldiers intercepted two vehicles carrying weapons whose suspected destination was Syria, Lebanese security sources said Wednesday.
Four Lebanese and six Syrian nationals were arrested over the suspected smuggling attempt, the sources told dpa.
In the Turkish city of Istanbul, Syrian opposition leaders wrapped up a two-day meeting, pledging unity under the umbrella of the Syrian National Council (SNC), a key opposition grouping.
Several Western and Arab powers have repeatedly called on the fractured Syrian opposition to project a united front. d