* Rebels dig in, defying ultimatum from Kiev to clear out
* Kiev threatens military action, accuses Moscow of stirring unrest
By Gabriela Baczynska
DONETSK, Ukraine, April 14 (Reuters) - Pro-Russian separatists occupying the regional government building in Ukraine's eastern city of Donetsk vowed on Monday to fan out and take control of strategic infrastructure across the province they have declared an independent "people's republic".
Defying an ultimatum from Kiev to surrender, some two dozen separatist leaders gathered for a strategy meeting in a dark top-floor room of the 11-storey building they have held for eight days.
"Everything from city cleaning to the sewage system, the airport, railway stations, military ... should all be under your control," Vladimir Makovich, one of the senior separatist leaders, told the group.
Donetsk, a province with 4.3 million people - 10 percent of Ukraine's population - and much of its heavy industry, is the biggest prize of the eastern regions where pro-Russian separatists have captured government buildings in the past week.
Kiev has threatened military action against separatists and accuses Moscow of organising the unrest its mainly Russian-speaking provinces to repeat the scenario in Crimea, a Black Sea peninsula Russian forces seized and annexed last month.
Makovich said public officials who wished to continue their work must switch allegiance.
"Not a single serious decision can be made without you," said Makovich, who wore a beard and denim jacket.
Not all of the rag-tag civilian militia of mostly masked men holding the building in Donetsk agree precisely on their demands, with some calling for broader autonomy within Ukraine and others wanting to join Russia right away.
But - clad in mismatched protective gear and armed with hunting rifles, knives, batons and steel rods - they are united in their disdain for Kiev and determination to stand their ground.
"One thing is clear, there will be no May 25 presidential elections for us," Denis Pushilin, the self-styled head of the "Donetsk People's Republic", declared, referring to plans for a vote Kiev hopes will finally restore normalcy to the country after months of unrest.
"The rest we are still working on."
READY FOR A FIGHT
Over the past week, the separatists have dug in, turning the massive Soviet-era building into a bastion for urban warfare.
Barricades crisscross the corridors and steel plates have been welded to some windows. The stale air hangs thick with cigarette smoke and the body odour of the men camped in its halls. Empty rooms are cluttered with smashed furniture.
During the day, women who sympathise with the men's cause come in and out, cooking meals, clearing away garbage and handling the paperwork for the separatists.
Alexander Zakharchenko, a 38-year-old commander of a paramilitary unit made up of members of a martial arts club from the eastern Ukrainian city of Kharkiv, said his men were staying sober to be ready for a fight.
"We are ready for storming at any time. No matter what happens this building will not be given up. It has become a symbol of our fight and we will protect it like a symbol," he said, adding there were some 1,500 fighters inside the building.
"Only idiots are not afraid. But to be afraid and to be cowardly are two different things. We will not be cowards." (Editing by Alissa de Carbonnel and Peter Graff)