The Syrian government ignored Arab powers' moves to halt its crackdown on a pro-democracy uprising as more opposition supporters and military personnel were killed in unrelenting violence.
The Syrian military said 10 personnel, including six pilots, were killed in an attack on an air force base and that the incident proved foreign involvement in the eight-month revolt against President Bashar al-Assad's rule.
Government forces shot dead at least four demonstrators in the capital Damascus who were appealing for foreign intervention to stop the crackdown, activists said.
Two other civilians were killed in raids on their homes, they said.
Earlier today, a deadline set by the Arab League for Syria to sign a deal allowing peace monitors into the country expired without any government response.
Turkey meanwhile said it could no longer tolerate any more bloodshed.
More than 3,500 people are estimated by the United Nations to have been killed since March, the majority of them civilians gunned down as they took to the streets of Syrian towns and cities to call for an end to Mr Assad's rule.
Under the Arab League initiative, Syria agreed to withdraw troops from urban centres, release political prisoners, start a dialogue with the opposition and allow in monitors.
The bloodshed did not stop and Arab foreign ministers said in Cairo on Thursday that unless Syria agreed to the monitors, they would consider imposing sanctions including halting flights, curbing trade and stopping deals with the central bank.
The League extended the deadline after it expired on Friday, saying they would wait until the day's end before deciding what to do.
The announcement of the air force attack appeared to be an oblique response.
"An armed terrorist group undertook an evil assassination plot that martyred six pilots, a technical officer and three other personnel on an air force base between Homs and Palmyra," a military spokesman said on state television.
"This confirms the involvement of foreign elements and their support of these terrorist operations in an effort to weaken the fighting capabilities of our forces," he said.
The account fits the government narrative that it is facing an armed insurrection by trouble-makers backed by its enemies, rather than a largely peaceful pro-democracy movement inspired by the Arab Spring revolts which toppled the rulers of Tunisia, Egypt and Libya this year.
A Syrian opposition member said the attack was an ambush on a military bus near Furqlous, 35 km southwest of Homs.
"Furqlous is a military region and it is not difficult for an insurgent guerrilla force to chose targets there," he said.
State television also showed pictures of thousands of people demonstrating in central Damascus "expressing their rejection of the Arab League decision against Syria".