"We're very concerned about what's happened and very concerned for the family of the two pilots who are missing," said EU foreign policy chief Catherine Ashton. "We will be obviously looking to Turkey to be restrained in its response."
The ministers were meeting in Luxembourg for a regular conference, a day before a scheduled NATO meeting to discuss how to react to Friday's incident, which Turkey says occurred in international airspace and without warning. Turkey is a member of NATO, but is only a candidate for membership of the European Union.
The ministers added one person and six companies and other entities to a sanctions list, an EU official said. So far, the EU has imposed asset freezes and visa bans on more than 100 people responsible for or associated with the violent repression against Syria's civilian population, and an asset freeze on 43 entities.
British foreign secretary William Hague called for increased pressure, but said the jet incident did not fundamentally alter the situation in Syria, where Assad has been suppressing a 16-month revolt against his rule.
"I don't think it illustrates a different phase," Hague said. "It's very important that we increase the pressure with additional sanctions. Other countries will be very active in arguing for a new resolution from the (United Nations) Security Council."
Russia and China, both permanent members of the U.N. Security Council with veto power, have blocked efforts by Western powers to condemn Assad or call for his removal.
Turkish prime minister Recep Tayyip Erdoğan has so far eschewed bellicose rhetoric, and has seemed to back away from any suggestion of an armed response.
Calling Tuesday's meeting, he invoked a NATO article providing for urgent consultations if a member considers its security interests threatened. Had he sought some kind of retaliation from the NATO meeting set for Tuesday, he could have invoked another article on mutual defence.
"Military intervention in Syria is out of the question," said Dutch foreign minister Uri Rosenthal. "It is not a matter of consideration for the Dutch government. That is also at stake in the ... context of NATO."
The United Nations has said more than 10,000 people have been killed by government forces, while Syria has said at least 2,600 members of the military and security forces have been killed by what it calls foreign-backed "Islamist terrorists."
The recent intensification of fighting has raised fears in Turkey of a flood of refugees and a slide into ethnic and religious warfare that could envelop the region. Ankara, like the West, is torn between a wish to remove Assad and the fear that any armed intervention could unleash uncontrollable forces.