By John Irish and Vladimir Soldatkin

PARIS/MOSCOW (Reuters) - France dismissed Russian suggestions on Friday its air strikes against oil installations in Syria were illegal, saying they were "an appropriate and necessary riposte" to attacks by Islamic State.

President Francois Hollande will travel to Moscow on Nov. 26 as part of an effort to create a grand coalition to fight Islamic State, despite differences over the future of Syrian President Bashar al-Assad, whose key backers are Russia and Iran.

Paris launched air strikes against the Islamist group's Syrian stronghold in Raqqa this week following attacks that killed 130 people in Paris on Nov. 13.

It has previously targeted oil installations under the control of Islamic State and said it aimed to cut the group's main revenue stream.

Russian Foreign Ministry official Ilya Rogachev earlier on Friday criticized France's justification for the attacks, that they were self-defense according to Article 51 of the United Nations Charter. He said that was misplaced because Paris had not sought approval from the Syrian government.

"We cannot support such actions because they are being carried out without an agreement of the Syrian government," he told Kommersant daily.

"The bombing of oil infrastructure is based on ... quite different reasons and they are not justified by self-defense," he added.

"As Bashar al-Assad and Islamic State are equal priority enemies for them, they inflict damage to both of them by such hits. Please note, the French do not bomb the same targets in Iraq."

France has called for Assad to step down after a political transition, and its Western allies have criticized Moscow for mostly focusing its raids in Syria against Western-backed rebel groups.

"The French strikes against oil sites controlled by Daesh (Islamic State) are part of legitimate self-defense," French Foreign Ministry spokesman Romain Nadal told reporters on Friday.

"They are a necessary and proportionate response to the attacks carried out by Daesh," he said.

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Russia this week launched massive strikes on Raqqa in response to confirmation that the group had blown up a plane full of Russian tourists over Sinai in Egypt.

On Wednesday Foreign Minister Sergei Lavrov said if the West wanted an international coalition against Islamic State, it must drop its demands for Assad's ouster.

(Reporting by John Irish; editing by Andrew Roche)