Syrian officials are blaming al-Qaeda militants for two deadly explosions in the capital Damascus.
Two car bombs were reportedly detonated close to security buildings, killing at least 40 people.
Dozens more are said to have been wounded.
It is the first such attack since a revolt against President Bashar al-Assad began nine months ago.
Members of an Arab League delegation visited the scenes of the explosions.
They arrived in Syria just 24 hours earlier to make preparations for a team of monitors, who – according to an Egyptian news agency – will arrive on Monday.
Meanwhile, amateur footage has emerged apparently showing a body being retrieved from a street in the city of Homs.
There was fighting in the area on Thursday.
Other footage reportedly captures the latest protests against President Assad.
The government claims it is fighting terrorists. Critics say the regime may have staged the Damascus attacks to reinforce its case.