Merkel also said it would be necessary to involve the regime of Syrian President Bashar Assad in talks.
Her comments show that support is broadening for military action in Syria and also that Assad will need to play a role at the negotiating table in discussions on ending the war.
The United States and its allies are involved in military action in Syria and Russia has also launched air strikes, saying on Saturday it would step them up.
Russia, Iran, Iraq and Syria earlier established a joint information center in Baghdad to coordinate their operations against Islamic State militants.
“The main goal of the center will be gathering, processing and analyzing current information about the situation in the Middle East – primarily for fighting ISIL,” a military-diplomatic source told Russian news agencies.