French President Francois Hollande was traveling to Moscow on Thursday to push for a stronger coalition against Islamic State militants in Syria, trying to unite France, the United States and Russia in the aftermath of the Paris attacks that killed 130 people and jolted the West.

Hollande’s visit comes two days after he met with President Barack Obama in Washington, where both leaders vowed to escalate airstrikes against IS and bolster intelligence sharing. Islamic State militants have claimed responsibility for the Nov. 13 attacks in Paris, as well as deadly bombings in Beirut and the downing of a Russian airplane on Oct. 31 that killed all 224 people on board over Egypt’s Sinai Peninsula.

Hollande’s difficult task became even more arduous after Turkey shot down a Russian warplane near the Syrian border on Tuesday. The incident underscored the complex military landscape in Syria, where a sprawling cast of countries and rebel groups are engaged on the battlefield and in the skies overhead, sometimes with minimal coordination.

The French president hopes to make progress on three priority issues: to prevent Syrian President Bashar Assad from targeting civilians, to focus the airstrikes on IS militants, not the moderate Syrian opposition and to move forward on a political transition in Syria.

France will also seek to “avoid an escalation” between Russia and Turkey, according to a French diplomatic official who spoke on condition of anonymity because of the sensitivity of the issue.

In advance of Hollande's meeting with Putin, France sought to dismiss concerns that it might soften its stance on international sanctions against Russia over Ukraine in exchange for Russia's cooperation in the fight against Islamic State militants. France's ambassador to the U.S., Gerard Araud, tweeted Tuesday evening that "Hollande has confirmed the sanctions will be maintained as long as the Minsk agreements are not implemented."

Following his meeting with the French president, Obama said Russian cooperation in the fight against the Islamic State would be "enormously helpful." Both Obama and Hollande, however, insisted that a political transition in Syria must lead to Assad’s departure. Russia, on the other hand, has been Assad’s staunchest ally.

Last week, Hollande called for the U.S. and Russia to set aside their policy divisions over Syria and "fight this terrorist army in a broad, single coalition." But his office acknowledges that "coordination" sounds like a far more realistic goal.

With two suspects of the Paris attacks at large, tensions were still high in Belgium on Thursday with the capital Brussels on the highest-level threat alert.

Authorities launched a raid in southern Belgium Thursday afternoon linked to the Paris attacks but did not detain any suspects.

In Brussels, a civil protection squad decontaminated several people as a precaution at the main mosque after a suspicious parcel arrived. The person who opened the package discovered white powder and immediately contacted the authorities. A specialized crew from the fire department was sent, witnesses at the scene said.

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Nataliya Vasilyeva in Moscow and Raf Casert in Brussels contributed to this report.