evidence: Explosions sounded before dawn in Kyiv and gunfire was reported in the city center as Western leaders scheduled an emergency meeting and Ukraine's president pleaded for international help to fend off an attack that could topple his democratically elected government, cause massive casualties and ripple out damage to the global economy. Among the signs that the Ukrainian capital was increasingly threatened, the military said Friday that a group of Russian spies and saboteurs was seen in a district of Kyiv about 5 kilometers (3 miles) north of the city center. Police told people not to exit a subway station in the city center because there was gunfire in the area. [...] As air raids sirens sounded in Kyiv before dawn Friday, guests of a hotel in the city center were directed to a makeshift basement shelter, lined with piles of mattresses and bottles of water. Workers, all local university students, served tea and cookies to the guests. Some people ducked out to a courtyard to smoke or get fresh air.