* Annan says waiting for answers from Assad
* Bodies found dumped in mosque as army pounds northern city
* Rebels kill soldiers in separate ambushes
* Assad calls parliamentary election; U.S. calls it "ridiculous"
* China offers aid, Wen says not taking sides
By Oliver Holmes and Erika Solomon
BEIRUT, March 14 (Reuters) - U.N.-Arab League envoy Kofi Annan kept up efforts to broker a halt to hostilities as Syrian government forces killed dozens of people in the northern city of Idlib, dumping their bodies in a mosque, opposition activists said.
While Annan waited for an answer from President Bashar al-Assad to his proposals to end the violence, the army intensified its assault on the province of Idlib near the Turkish border, intermittently shelling built-up areas and spraying houses with machinegun fire in a bid to dislodge anti-government fighters.
The rebels said they had hit back, killing some 22 soldiers in two separate ambushes.
Clashes were reported in the eastern city of Deir al-Zor and security forces shelled Homs, Syria's third largest city, as the year-long uprising against President Bashar al-Assad's authoritarian rule increasingly came to resemble a civil war.
The United Nations says more than 8,000 people have died in the uprising and its refugee agency said on Tuesday that some 230,000 Syrians had fled their homes during the past 12 months, of whom around 30,000 have sought safety abroad.
In an apparent bid to deter the exodus, Syrian forces have laid landmines near its borders with Lebanon and Turkey along routes used by refugees to escape the mayhem, advocacy group Human Rights Watch said.
Speaking after meeting opponents of Assad in Turkey, Annan said he was expecting to hear a response from Syria later on Tuesday to "concrete proposals" he had made to end the escalating violence.
But by evening there was no word on an answer, although the Syrian parliament said Assad had ordered a legislative election for May 7. It will be held under a new constitution, approved by a referendum last month which the opposition and their Western and Arab backers dismissed as a sham.
Russia and China have welcomed Assad's reform pledges, including the promised election, and have blocked moves in the United Nations to censure the Syrian leader.
Chinese Premier Wen Jiabao said on Wednesday that Beijing was taking no sides in the crisis, and that he was "deeply pained" by the suffering of the Syrian people, though his remarks did not suggest China's diplomatic position will change.
Earlier, state media said China will offer $2 million in humanitarian aid through the Red Cross.
Russian Foreign Minister Sergei Lavrov said on Tuesday that Syrian government forces would not stop fighting or withdraw from their positions unless rebel forces instantly mirrored their move.
The U.S. State Department was dismissive of Assad's election plan: "Parliamentary elections for a rubber-stamp parliament in the middle of the kind of violence that we're seeing across the country? It's ridiculous," spokeswoman Victoria Nuland said.
After a crackdown in the central city of Homs, the army has intensified its operations in the north and has been shelling the town of Idlib for the past three days.
An activist in the town, speaking by telephone, said security forces had killed more than 20 people trying to leave the area in the past two days and dumped their bodies in al-Bilal mosque. When locals went to inspect the corpses, they too came under fire, pushing the death toll above 50, he said.
Another activist gave a slightly lower death toll.
"When people came from the neighbourhood early this morning, the security forces also started firing at them. In total, about 45 people were massacred," said the man, who like many in Syria gave only his first name, Mohammed, for fear of reprisals.
Reports from Syria cannot be independently verified as the authorities deny access to rights groups and journalists.
Video footage showed the bodies of several unidentified men strewn on the floor of the mosque.
Army defectors killed at least 10 soldiers in an ambush in Idlib region, while rebels also killed 12 members of the security forces in the southern town of Deraa, according to the British-based Syrian Observatory for Human Rights.
Following meetings with Assad at the weekend in Damascus, former U.N. chief Annan held talks in Ankara with the Syrian National Council (SNC) - a fractious assortment of Assad opponents whose leadership lives abroad.
Abdel Baset Seda, a member of the SNC's executive council who attended the meeting, said Annan had been reluctant to detail what he had proposed to Assad.
"But he (Annan) told us that the proposals included some questions and that he is awaiting al-Assad's responses to them and that he had plans depending on whether the responses came in positive or negative," Seda told Reuters by phone from Turkey.
Seda added: "He (Annan) spoke with us about the humanitarian situation in Syria and how to deliver emergency aid into Syria to help the people and also spoke about the idea of sending international monitors."
The United Nations said on Tuesday that it would soon deploy human rights monitors in countries bordering Syria to collect eyewitness testimony on atrocities committed in the country.
The SNC itself is deeply divided, as the resignation of three prominent members from the council on Tuesday showed.
Haitham al-Maleh, a former judge and long-standing dissident against four decades of Assad family rule, was joined by opposition leader Kamal al-Labwani and human rights lawyer Catherine al-Talli in announcing their resignation.
Syria lies in a pivotal position, bordering Turkey, Jordan, Israel, Iraq and Lebanon. Its 23-million population comprises a mix of faiths, sects and ethnic groups, and analysts say the gathering conflict could destabilise the entire region.
On Tuesday, the Organisation of Islamic Cooperation (OIC), the world's largest Islamic body, said it had received permission by Damascus to send humanitarian aid to Syria, and will send a team there soon to assess the population needs.