Fierce fighting surged Friday in eastern Ukraine as Russian-backed separatists mounted a major, sustained offensive to capture a strategic railway hub ahead of a weekend cease-fire deadline. At least 25 people were killed across the region, officials reported. Clashes appeared only to have increased since a peace agreement was sealed Thursday in the Belarusian capital of Minsk by the leaders of Russia, Ukraine, Germany and France. But the pending cease-fire only appeared to spark a last-minute grab for territory that left at least 25 people dead. The government-held railway town of Debaltseve was on the receiving end of dozens of artillery and rocket salvos in the 24-hour period following the Minsk talks, Ukrainian military officials said.