Pro-Russian separatists, who have besieged a number of government buildings in Ukraine's eastern districts, have turned down an amnesty offer handed by the government, stocking fear that a 48-hour ultimatum may end with violence.
The government said it would not prosecute pro-Russian separatists if they surrender their weapons, but the armed men said they would not leave.
Fortifying barricades around the buildings with barbed wire and sandbags overnight, they said the government will have to first accept holding a referendum on self-rule, before they evacuate the buildings.
The government said it would storm one of the buildings in Luhansk unless protesters leave by the end of the day, Al Jazeera was informed.
An armed storming of the buildings could provoke a strong response from Moscow, which has reserved the right to send troops in to protect Russian speakers.
In Donetsk, pro-Russian armed groups have already declared the district a "people's republic".
Tensions have risen in the mainly Russian-speaking east since the overthrow of Ukraine's Moscow-backed president and the installation of a new pro-European government, which says the occupations are part of a Russian-led plan to dismember the country.
The interior minister on Wednesday said he expected the situation to be brought under control within 48 hours, with force if necessary.
But Acting President Oleksandr Turchynov struck a softer tone on Thursday, saying he hoped to avoid bloodshed.
"We need to resolve this situation with the minimum number of victims," Turchynov told parliament.
The seizure of government buildings in February gave separatists control of the Crimea region and led weeks later to its annexation by Russia.
While some of the activists say they only want their regions to have more independence without leaving Ukraine, others have described the referendum as a step on the way to union with Russia.
Activists at both buildings said they would continue talks with the government, but said the current offer was not enough.
"They offered amnesty, but there is no movement on a referendum for federalisation," said Alexander Gureyev, one of the activists barricaded into the five-storey former KGB headquarters in Luhansk.
"We are not going to accept an amnesty without a referendum."
Around 250 protesters, some waving Russian flags, braved cold rain outside the building to show their support.
Activists armed with automatic rifles, pistols and knives kept guard on the building, pushing bookshelves against the windows so no one could see inside. One protester put their arsenal at around 200-300 rifles.
A larger crowd of around 1,500 people surrounded the seized regional government building in Donetsk, where activists also rejected the president's offer.