Tensions are again growing in Ukraine as trouble spreads to the south of the country and the former president is reported to be in Russia.
The latest trouble began when a group of armed men took over government buildings in Crimea, which is in the south of Ukraine.
The group then raised Russian flags outside the building.
This is a challenge to the new authorities in Ukraine, because they want the country to move away from Russia's influence.
The areas around the occupied buildings have been sealed off by police.
Crimea is the only Ukrainian region where most of the people that live there are Russian.
Escape to Russia
Meanwhile, Ukraine's former President Viktor Yanukovych has fled to Russia, and the authorities there say they will protect him.
Mr Yanukovych is wanted by the police in Ukraine over the deaths of dozens of protesters.
This growing tension has led to both the Ukrainian and Russian leaders to announce that their militaries are 'on alert'.
Arseniy Yatsenyuk was confirmed as Ukraine's new Prime Minister on Thursday afternoon.
Voting has been taking place throughout the day to appoint new cabinet members.
Mr Yatsenyuk said: "We ask our Russian partners to... stick to their obligations, we believe Russia would never intervene into Ukrainian domestic affairs and will refrain from any steps that would split Ukraine.
"We are committed to having Ukraine as one united country. We will punish anyone for separatism in Ukraine with all legal and constitutional means," he added.
Concerned by Crimea
British Prime Minister David Cameron says he is concerned by what is happening in Crimea and has warned Russia that 'the world will be watching'.
He said Russia should respect Ukraine's independence.
The United States has also called on the Russian government not to get involved in Ukraine.
US Defence Secretary Chuck Hagel told Russia "not to take any steps that could be misinterpreted, or lead to miscalculation, during a very delicate time".
The Ukrainian population is still very much divided between people who are loyal to Russia and people who are pro-Europe.Tensions are again growing in Ukraine as trouble spreads to the south of the country and Russia vows to protect the country's former President.
Guide: What's happening in Ukraine?