Four soldiers and one rebel fighter were killed in fresh fighting between Ukrainian forces and Russian-backed insurgents on Sunday, the bloodiest clash in weeks in the war-torn country's east.
The last spike in violence was reported in mid-December, leading the State Department to express concerns about casualties resulting from a "Russian-separatist attempt to seize additional Ukrainian territory" in areas near Donetsk.
The separatist website DAN said on Monday shelling by Ukrainian troops had killed one female civilian and wounded three others in the rebel-held town of Makiyivka, south of Avdiyivka.
The conflict has claimed over 9,600 military and civilian lives since it began in 2014, the United Nations Human Rights Office reported. An earlier peace deal, known as Minsk II and brokered in February 2015 by Russia, France and Germany in Minsk, Belarus, reduced ground combat between Ukrainian troops and pro-Russian rebels but did not end it.
The rebels began attacking government positions in the eastern frontline town of Avdiyivka on Sunday, Ukrainian officials said. "The enemy continues to fire at our positions with heavy artillery and mortars", Oleksandr Motuzyanyk, a spokesman for Ukraine's military, told reporters on Monday.
The violence came as Ukrainian President Petro Poroshenko urged German Chancellor Angela Merkel to step up economic sanctions, as fears grew in Kiev that United States support could wane if President Donald Trump draws closer to Russian leader Vladimir Putin.
Electricity has been off since Sunday and water supplies are sporadic amid the shelling and gunfire.
Ukraine has been wracked by conflict since April 2014 following Russia's annexation of Crimea from Ukraine. Russian Federation has denied backing the rebels.
The latest clashes came ahead of talks between President Petro Poroshenko and German Chancellor Angela Merkel in Berlin on January 30.