Ukraine's new prime minister demanded that Russian President Vladimir Putin pull back his military Sunday, as Ukraine called up all military reserves and Western powers angrily warned Moscow over Russia’s incursion into Ukrainian territory.

"This is not a threat: This is actually the declaration of war to my country," said Prime Minister Arseniy Yatsenyuk, who heads the pro-Western government that took power in Ukraine after massive protests forced President Viktor Yanukovich, a Russian ally, from power a week ago.

Hours later, pro-Russian troops overtook a ferry terminal on the easternmost tip of Crimea, which serves as a common departure point for many Russian-bound ships.

The seizure of the terminal in the Ukrainian city of Kerch, about 12 miles, or 20 kilometers by boat to Russia, exacerbated fears that Moscow is planning to bring more troops into this strategic Black Sea region, as the West debates how to react to the incursions.

By early Monday, soldiers were operating the terminal. The men refused to identify themselves, but they spoke Russian and the vehicles transporting them had Russian license plates.

Yatsenyuk’s remarks came as a convoy of Russian troops rolled toward Simferopol, the capital of Ukraine's partially autonomous Crimea region, a day after Russian forces took over the strategic Black Sea peninsula without firing a shot. The area has a large number of ethnic Russians, many of whom feel culturally and ideologically close to Russia. Some have even called for Moscow to come to their aid after the country’s recent change to a more pro-Western government.

Also on Sunday, Russian forces surrounded several small Ukrainian military outposts in Crimea and demanded that Ukrainian troops disarm. Some refused, and though there was no fighting the situation remained tense.

Ukraine’s new government has called up all military reserves, and a senior security official said Sunday it was vital for the country’s military to be combat-ready as soon as possible.

Ukrainian officials said Sunday that the country’s navy still has its full fleet of 10 ships in the Crimean port of Sevastopol, and that the craft have not been disarmed and remain loyal to Kiev. However, a statement made hours later said Ukraine had fired its navy chief and launched a treason case against him for refusing to fight the Russians. It also accused the chief of surrendering Sevastopol headquarters.