In Kyiv, a summit between EU and Ukrainian officials got underway on Tuesday, with European Commission President Ursula von der Leyen promising to ensure Ukraine's natural gas supply.

"We will also work closely with you [...] to increase gas supply capacity coming from member states of the European Union," von der Leyen said in a statement.

Her comments on gas supply come amid strong opposition in Ukraine to the new Nord Stream 2 gas pipeline between Russia and Germany. 

Von der Leyen also committed to Ukraine's sovereignty and the Minsk agreements. Signed in 2014 and 2015, they sought to end Russia's war in eastern Ukraine.

Ukrainian President Volodymyr Zelenskyy is hosting European Council President Charles Michel and von der Leyen, along with other EU officials.

They are discussing the worsening situation in eastern Ukraine as well as seeking to further strengthen economic and political ties.

What else is being discussed?

In addition to pledges to ensure Ukraine's energy security, the EU's foreign affairs chief Josep Borrell met with Ukraine's Foreign Affairs Minister Dmytro Kuleba.

"The EU stands firmly behind Ukraine's sovereignty and territorial integrity," Borrell tweeted following the meeting.

Tensions between Ukraine and neighbor Russia escalated again this year after Russian troops amassed on the Ukrainian border.

The EU and Ukraine also signed an aviation agreement to open the country to more low-cost air routes and boost tourism.

Ukraine fears energy security

The Nord Stream 2 pipeline transports gas directly from Russia to Germany, bypassing Ukraine and other central and eastern European countries.

Ukraine is concerned that the pipeline's path will cause it to miss out on gas transit fees. This is despite a deal from Germany that sets out plans to boost investment in the country. Ukraine is also worried that the pipeline could increase Russia's political leverage in the region.

Further energy concerns sparked a bilateral row between Ukraine and its EU neighbor Hungary last month, after Budapest signed a new long-term energy deal with Russia that sidelined Ukraine as a transit country. The deal also brings into question Ukraine's ability to take reverse flows of Russian gas from Hungary.

This is story will be updated as more details become available.

kmm/aw (Reuters, dpa)