Ukraine said Tuesday that the leaders of Germany and France had agreed to back "firm" steps against Russia should pro-Moscow rebels hold disputed elections in the ex-Soviet state's separatist east.

A top aide to President Petro Poroshenko said German Chancellor Angela Merkel and French President Francois Hollande had agreed at trilateral talks in Berlin on Monday to a set of "red lines" Russia must not cross.

French President Francois Hollande said Tuesday that the "neutralization" of Syrian leader Bashar Assad was a precondition to resolving the crisis in the war-torn country.

"We must reduce the terrorist influence without maintaining Assad. The two are bound up together," Hollande told a gathering of French diplomats in Paris.

French investigators had just hours left on Tuesday to decide whether to charge a Moroccan gunman who was overpowered by a group of Americans and a Briton when he opened fire on a crowded Paris-bound train.

Ayoub El Khazzani, a 25-year-old who boarded the high-speed train in Brussels on Friday armed with a Kalashnikov assault rifle, a Luger automatic pistol, ammunition and a box-cutter, is being questioned by counter-terrorism investigators.

French President Francois Hollande offered Tuesday to organize an international meeting on tackling jihadist group Boko Haram that has killed thousands in Nigeria.

"In several days, I will receive the new Nigerian President (Muhammadu) Buhari and I will confirm to him that France is ready to unite all the actors in the fight against Boko Haram," Hollande said during a speech to diplomats on Tuesday.

President Francois Hollande warned Tuesday that France must brace for further attacks, just days after a potential bloodbath on a train was foiled by passengers.

"We are still exposed," Hollande told diplomats gathered in Paris.

A new wave of migrants began entering the European Union from Serbia Monday as the leaders of France and Germany called for a unified response to the continent's biggest migrant crisis since World War II.

The EU has been struggling to find a response to the unprecedented numbers arriving -- from the thousands landing on the shores of Greece and Italy to the hundreds risking their lives to climb onto trucks to travel from France to Britain.

A Sudanese man who allegedly walked almost the entire length of the undersea Channel Tunnel from France to Britain pleaded not guilty Monday to charges in an English court.

Abdul Rahman Haroun, 40, appeared at Canterbury Crown Court in Kent, southeast England, via video link from a prison in the county.

President Francois Hollande bestowed France's highest honor on a group of Americans and a Briton on Monday saying the whole world "admires their courage and cool composure" in overpowering a Moroccan gunman on a crowded train.

Anti-terror investigators were questioning the alleged attacker, 25-year-old Ayoub El Khazzani, who boarded the high-speed train in Brussels bound for Paris on Friday armed with a Kalashnikov assault rifle, a Luger automatic pistol, ammunition and a box-cutter.

A heavily armed man opened fire on a high-speed train traveling from Amsterdam to Paris on Friday, injuring two people before being overpowered by two American passengers.

The motives behind the attack were not immediately known, although French prosecutors said a probe was being launched by counter-terrorism investigators.

French officials have been holding talks with their counterparts in Beirut away from the media spotlight to follow up the delivery of French weapons to the Lebanese army under a Saudi grant, al-Joumhouria daily reported on Friday.

Lebanon received in April the first shipment of $3 billion worth of French arms under the Saudi-financed deal to boost the country's defensive capabilities to combat terror threats.