LONDON—Stock markets fell on Thursday after Russian-backed separatists and Ukrainian government forces accused each other of firing shells, sending traders to seek safety in government bonds, and pushing gold prices to a new eight-month high. The two sides traded accusations each had fired across the ceasefire line in eastern Ukraine, raising alarm at a time when Russia has massed more than 100,000 troops close to Ukraine’s borders. The West accuses Russia of preparing for an invasion, while Moscow says it is pulling back some troops and accuses Kyiv of planning an escalation to try to recapture rebel-held territory by force. Losses on stock markets were widespread, though not as big as in recent sessions. In Europe, the Euro STOXX had slipped 0.1 percent by 1150 GMT while Britain’s FTSE 100 dropped 0.65 percent. Strong corporate earnings in Europe helped keep the losses in check. Wall Street futures pointed to a …