Ukraine, Georgia, and Moldova have signed pacts with the European Union, binding them closer together both politically and economically.
The “association agreements” commit the countries to EU regulations, standards, quality controls and free market competition.
Russia had warned of grave consequences if any of the former Soviet states signed the agreement.
It was former Ukrainian President Viktor Yanukovych’s decision not to sign the pact under pressure from Moscow that ignited the protests that eventually led to his downfall and the current crisis in the country.
Ukrainian President Petro Poroshenko called the pact a historic “symbol of faith and unbreakable will”, which underlines Ukraine’s “sovereign choice in favour of membership of the EU”.
European Council President Herman Van Rompuy hailed the pact as a “great day for Europe” and a demonstration that teh EU stands alongside the eastern European states.
The agreement has been signed as the temporary ceasefire between pro-Russian rebels and the Ukrainian military comes to an end in east Ukraine later today.
The UN estimates that at least 423 people have died in the conflict in east Ukraine since 15 April.