Military intervention in Syria will not solve the worst humanitarian crisis in a generation, a leading relief charity said.
Some 100,000 lives have been lost during the conflict and two million people have fled the country, Oxfam Ireland said.
The organisation called for a renewed political effort to secure dialogue through the UN and at this week's G20 meeting of world leaders in St Petersburg.
Chief executive Jim Clarken said: "The UK Government should concentrate its efforts on a political solution to this crisis and we also call on the Irish Government to continue to make its voice heard in the crucial days ahead."
Volunteers in Belfast laid white flowers among rows of white "gravestones" to highlight the bloodshed.
Mr Clarken said Oxfam opposed the use of force by members of the international community.
"The best means of protecting civilians from violence is to urgently pursue a political solution that provides the best and only hope to end the conflict once and for all," he said.
MPs defeated a Government motion on military action and the US Congress is expected to vote on the issue soon.
Oxfam has helped more than 200,000 people affected by the Syrian violence and hopes to reach 650,000 by the end of the year in Jordan, Lebanon and Syria.