Sima Solomonova, the head of the international human rights group Memorial, told reporters in Geneva last week in a closed-door meeting: “The people on the ground are very scared. There are no signs of hope.”

Humanitarian agencies warn the fighting in the east will be “worsening, with refugees and internally displaced people coming back home in large numbers.”

Russia’s Ministry of Foreign Affairs said on Thursday it had warned Ukraine and western countries about “the need to consider military action” against pro-Russian separatists in eastern Ukraine if the operation becomes harder.

On Wednesday, Russian Foreign Minister Sergei Lavrov blamed Ukraine for the escalation in the fighting, which has taken on some of the most dramatic details of the early months of the Ukrainian conflict, including the first shelling of the eastern city of Mariupol and multiple shootings of government troops near the city of Horlivka on Thursday.

But Ukrainian officials have been reluctant to lay the blame squarely at the feet of the separatists.

There is mounting evidence the conflict is becoming far more bloody and vicious, with large sections of Donetsk and Luhansk regions still completely shut off from the outside world.

Despite the latest escalation of fighting in eastern Ukraine, President Viktor Yanukovych has resisted calls for his immediate departure from Kiev, blaming the current economic crisis in the country and the war with Russia for the crisis.

The Russian Embassy in Kiev issued a statement that echoed Yanukovych’s sentiments on Wednesday, saying: “As one government, we have no wish to provoke further conflicts with the government in Kiev.”

The war in Ukraine has sent shockwaves through Europe and caused diplomatic rows in some of the former Soviet governments, with EU foreign ministers meeting in Brussels on Wednesday to try and find a diplomatic way forward.

In Ukraine itself, fighting has been joined by separatist troops who are now trying to move further into government-held territory despite Ukrainian government requests to stop.

A Ukrainian general named as General Valery Bolotov was killed in the past couple of days near the airport of Slovyansk, the separatist city in eastern Ukraine that has been the scene of heavy fighting between Ukrainian military and pro-Russian rebels in recent weeks, a Reuters correspondent said.

The government in Kiev said on Wednesday that it had killed 12 separatist soldiers and seized the headquarters of the separatist Luhansk People’s Republic last week.

More than 6,000 people, including about 1,700 rebels