Ukrainian forces attacked the rebel-held city of Slaviansk before dawn on Friday and pro-Russia separatists shot down at least one attack helicopter, killing a pilot, in a sharp escalation of the conflict. Describing the use of anti-aircraft missiles as proof of the presence of Russian special forces in the town that has become the military stronghold of the pro-Moscow movement, Ukrainian officials said Slaviansk was “tightly surrounded” and called on separatist leaders to release hostages and surrender. Reuters journalists in the city of 130,000 heard shooting from shortly after 4 a.m. (9 p.m. EDT Thursday) and saw a military helicopter open fire. Ukrainian troops could be in seen in armored personnel carriers in a southern suburb. The SBU security service said one military Mi-24 helicopter gunship had been shot down, killing one airman while a second had been taken prisoner by the rebels. It said […]