European leaders pledged to respond to "hybrid attacks" at the European Union's borders at the end of a two-day summit in Brussels but couldn't agree on a coordinated response.

Countries such as Poland and Latvia have reported a spike in the number of migrants crossing into the EU illegally from Belarus in recent months. 

Some leaders, including Lithuania's president, used the meeting to push for a border wall to be built along the EU's eastern frontiers. 

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However, there was strong opposition to the idea from the European Commission's own president. 

"I was very clear that there is a longstanding view in the European Commission and in the European Parliament that there will be no funding of barbed wire and walls," said Ursula von der Leyen. 

The EU has accused Belarus of flying migrants in from countries in the Middle East before helping them to reach the borders of EU nations, which Minsk denies. 

While European Council President Charles Michel had said the meeting would only "touch upon" it, leaders spent two hours debating Poland and the rule of law on Thursday. 

Earlier this month, Poland's Constitutional Tribunal ruled that some EU treaties are not compatible with the country's constitution. That challenged a cornerstone of the bloc's legal framework – that EU law takes precedence over national law in member states. 

At this week's summit, Michel said there needs to be "political dialogue" to find solutions. The European Commission has vowed it will respond to Warsaw but is still weighing up its options. 

Heading into the meeting, Spain's Prime Minister Pedro Sanchez had called for urgent action on rising energy prices as the continent heads into winter. He proposed member states could start buying natural gas collectively, boosting their bargaining power.

However, the Council's conclusions fell short of any direct action at the EU level. The European Commission will now explore joint procurement and a strategic gas reserve before the next summit in December. For consumers struggling to pay sky-high energy bills before Christmas though, the EU's measures could be seen as too little, too late.

WATCH: Angela Merkel and Ursula von der Leyen attempt a handshake

This week's summit was German Chancellor Angela Merkel's 107th EU summit and almost certainly her last. She has been in a caretaker role since the recent German elections, with political parties currently in the midst of negotiating a new coalition. 

In a tribute speech, European Council President Charles Michel described her as a "monument." Former US President Barack Obama also sent a special video, saying Merkel has an "unrelenting moral compass."