Russia may face new EU sanctions over support to separatist rebels in the east of Ukraine.
EU foreign ministers are meeting in Brussels on Thursday to debate fresh sanctions, on top of the already existing asset freezes and travel bans on Russian officials and Ukrainian separatist leaders.
"If we see no signs of improvement we should proceed with further sanctions," Lithuanian Foreign Minister Linas Linkevicius told the BBC.
"How many people should be killed in order to realise that lines were crossed many times?"
The US also indicated it is considering further sanctions.
"As long as Russia continues its blatant disregard of its obligations... the costs for Russia will continue to rise," US Vice President Joe Biden is reported to have told Ukrainian President Petro Poroshenko, during a phone conversation on Wednesday.
At least 30 people were killed in rocket attacks in the city of Mariupol in the east of Ukraine last week, as pro-Russian rebels announced a major offensive.
The attacks were widely condemned, including by the EU who warned “would inevitably lead to a further grave deterioration of relations between the EU and Russia”, according to EU foreign affairs chief Federica Mogherini.
Rocket attacks targeting Ukrainian civilians amount to war crimes says UN (26 January 2015)
EU foreign ministers to discuss increased pressure on Russia (25 January 2015)
Thirty dead in Ukraine rocket attacks (24 January 2015)