Greece geared up for a snap election next month, with an opinion poll showing the leftist party Syriza ahead despite a wave of defections over the country's massive new bailout.
Interior and transport ministers from EU countries are to hold talks in Paris to discuss security measures following last week's attack on a high-speed train that was foiled by passengers.
The EU sharply criticised Russia on Tuesday for the jailing of Ukrainian filmmaker and Kremlin critic Oleg Sentsov, calling it a violation of international law.
German Chancellor Angela Merkel and French President Francois Hollande called for a "unified" response to the worst refugee crisis to hit the EU since World War II.
Europe's interior and foreign ministers will meet in mid-October to discuss how to respond to the huge influx of migrants and refugees arriving at EU borders.
EU border agency Frontex reported a record 107,500 migrants at the European Union's borders last month, as the 28-member bloc struggles to cope with a refugee crisis
German Foreign Minister Frank-Walter Steinmeier urged the European Union to negotiate with Switzerland on Bern's plans for new quotas on immigration from the bloc.
Greek Prime Minister Alexis Tsipras warned that a German proposal to give his debt-ridden country a bridging loan rather than agree a new bailout would be "a return to a crisis without end".
The EU on Monday denounced an arson attack on armoured vehicles belonging to OSCE observers monitoring a fragile ceasefire in rebel-held eastern Ukraine.
The EU formally extended until next year a multi-million-euro aid package to help European fruit and vegetable growers hit by Russian sanctions over the Ukraine crisis.