By Dan Peleschuk and Tom Balmforth KYIV (Reuters) -Ukrainian forces are facing waves of assaults by Russian forces on the small salt-mining town of Soledar, Kyiv officials said on Tuesday, as Moscow strives to make its first breakthrough in the east in months. Britain’s Defence Ministry said Russian troops and mercenaries of the Wagner group were probably now in control of most of the town after advances in the last four days. Seizing Soledar would give an advantage to Russian forces as they fight to capture the city of Bakhmut, a few kilometres (miles) to the southwest. Troops from both sides…