(Refiles to fix spelling of dateline) By Serhiy Takhmazov TRAVNEVE, Ukraine (Reuters) – Government troops in front-line trenches in Ukraine’s east said on Monday heavy weapons fire from Russian-backed separatists had intensified to provoke all-out conflict amid fears of Russia seeking a pretext for a full-scale invasion of Ukraine. Ukrainian troops have battled Russian-backed forces in the Donetsk and Luhansk regions bordering Russia since 2014 in a conflict that Ukraine’s leadership says has killed 15,000 people. A ceasefire deal in 2015 staunched the worst fighting, but shelling has intensif…