European Commission chief Ursula von der Leyen on Tuesday named a new team to lead the European Union's most powerful institution for the next five years, focused on tackling challenges to the region's security, competitiveness and growth.

Lithuania's Andrius Kubilius will be the EU's first defence commissioner, with the new role designed to build up European military manufacturing capacity in the face of Russian aggression in Ukraine, on the bloc's eastern flank.

Spain's Energy and Environment Minister Teresa Ribera will be the new antitrust chief tasked with reining in the power of Big Tech and also ensuring that the EU achieves its green goals.

"The whole college (Commission) is committed to competitiveness," von der Leyen told a press conference, with the aim being "building a competitive, decarbonised and circular economy, with a fair transition for all."

Climate change "is the major backdrop of all what we are doing," von der Leyen said.

But, compared to her first five-year term, "the topic of security, triggered by the Russian war in Ukraine, but also the topic of competitiveness, have ... much more impact," she said.

The European Commission has the power to propose new EU laws, block mergers between companies and sign free trade deals.

All candidates will undergo hearings with lawmakers in the European Parliament who have to sign off on their nomination.

Each of the 27 member states will have one seat at the Commission's table, a role comparable to a government minister, although its political weight varies greatly depending on the portfolio.

The EU's two biggest countries have top jobs in the Commission - von der Leyen is German, and France's outgoing foreign minister Stephane Sejourne will be in charge of the key portfolio of industrial strategy.

Poland's nominee Piotr Serafin was appointed to the powerful job of overseeing the EU's budget.