The European Union has readied a draft statement for the foreign ministers of its 28 members to agree to add new names to the sanctions list and extend the sanctions by six months. Foreign ministers will meet at an extraordinary summit on Thursday following an escalation of the conflict in eastern Ukraine in recent weeks.

Pro-Russian rebels have made a number of advances, seizing the airport outside of Donetsk and launching an assault on the port city of Mariupol.

"In view of the worsening situation, the Council (of foreign ministers) agrees to extend the restrictive measures targeting persons and entities for threatening or undermining Ukraine's sovereignty and territorial integrity...until September 2015," said a draft conclusion for the meeting, as cited by Reuters news agency.

The statement refers to Russians and Ukrainians already subject to asset freezes and travel bans, that were initially put in place after Moscow annexed Crimea from Ukraine in March 2014.

The minister will also send a request to the European Commission asking that it to draw up a list of additional names that could be considered for sanctions.

The draft also noted evidence that Russia had given increased support to the separatists, which underlined Moscow's responsibility for the crisis.

More than 5,000 people have been killed in the conflict that erupted in April 2014, according to UN figures.