Top EU official Donald Tusk warned it would be "very, very tough" to reach a deal on reforms Prime Minister David Cameron has asked for to help keep Britain in the bloc.
EU leaders were considering holding a summit with Turkish President Recep Tayyip Erdogan later this month to seek his help in curbing migrant flows to Europe.
Tens of thousands of protesters poured into Warsaw's streets for a demonstration organised by the far-right, marching under the slogan "Poland for the Polish" and burning an EU flag.
EU regulators have given Volkswagen 10 days to clarify its own admission that nearly a million of the company's cars emit more CO2 pollution than originally claimed.
Prime Minister David Cameron said he was confident of achieving four key objectives in renegotiating Britain's EU relationship but warned the UK would have to "think again" about membership if they were not met.
EU leaders will push their wary African counterparts to help tackle the migration crisis at a summit in Malta this week, offering them billions of euros in aid in exchange for cooperation
The EU's economic affairs commissioner, Pierre Moscovici, voiced confidence that Greece would reach a "compromise" with its creditors by the end of the week on remaining reforms demanded under its third bailout.
EU president Donald Tusk urged Turkey to show its readiness to work with Brussels on issues such as the migrant crisis following a stunning election win by the party of President Recep Tayyip Erdogan.
Eurogroup chairman Jeroen Dijsselbloem said the fallout from the refugee crisis should be considered when assessing some members' budgets, adding it had already had a major impact on debt-ridden Greece.
The EU, desperate for help to solve the migrant crisis, has little option but to deal with Turkish President Recep Tayyip Erdogan on his own terms after a stunning election victory.
The European Union said it looked forward to working with the new Turkish government after elections showed the people's "strong commitment" to democracy.
EU foreign policy chief Federica Mogherini urged Israel Premier Benjamin Netanyahu and Palestinian president Mahmud Abbas to meet Quartet representatives "within days" in the hope of kick-starting stalled peace talks.
European Commission chief Jean-Claude Juncker backed Angela Merkel's welcoming stance towards migrants ahead of a mini-summit of leaders this weekend aimed at tackling record arrivals.
European Commission chief Jean-Claude Juncker chided EU member states for not respecting their pledges of humanitarian aid to tackle the migrant crisis, saying "urgency" was needed.
British Prime Minister David Cameron said he would unveil his long-awaited EU renegotiation demands early next month, amid growing impatience from his European partners.
European Union nations have agreed to suspend sanctions against Belarus after elections won by authoritarian President Alexander Lukashenko passed off without incident.
British Prime Minister David Cameron welcomed German Chancellor Angela Merkel to his country residence to discuss Britain's future in the European Union, amongst other topics.