Russian troops surrounded a military base in Ukraine's Crimea region Sunday in a tense standoff as the security crisis in the region worsened, NBC news reported. Armed men arrived at the base in Perevalne and demanded the Ukrainian soldiers surrender their weapons. The Ukrainian forces remained defiant, but were heavily outnumbered. No shots were fired in what appeared to be the first direct confrontation between Russian and Ukrainian military forces. Russian troops ave taken over Crimea without resistance and with the backing of most of this region's people. In the regional capital, Simferopol, a pro-Russian self-defense force protected a statue of Lenin and people were seen weaving Russian flags. Earlier Sunday, Ukraine's interim leaders called up military reservists, put their army on combat alert and appealed to the West for help. Ukraine also launched a treason case against the head of the navy, who surrendered his headquarters on Sunday in the Crimean port of Sevastopol — on only his second day on the job.