KIEV Ukraine accused pro-Russian rebels on Monday of carrying out the heaviest artillery attacks on government positions in six months and warned of signs the conflict was escalating despite a ceasefire deal.
The military said 400 rebel fighters supported by tanks had attacked government forces around the village of Starohnativka, 50 km (30 miles) north of the Kiev-held port city of Mariupol. The rebels denied attacking government troops.
Control of Mariupol could help the rebels form a corridor to the Crimea peninsula, which Russia annexed from Ukraine last year.
A ceasefire deal, signed in mid-February, has failed to stem the violence in the eastern conflict zone. Both sides regularly accuse the other of violating the terms of the peace agreement and casualties are reported almost daily.
"This brazen attack by the occupiers took place against a background of an escalating situation in east Ukraine," military spokesman Andriy Lysenko said, describing rebel shelling in the past 24 hours as the heaviest since a battle for the town of Debaltseve in February.
Ukrainian troops halted the offensive using artillery and regained lost ground, Lysenko said.
Senior separatist commander Eduard Basurin denied the rebels had attacked government troops and accused Ukraine of intensive shelling, rebel press service DAN reported.
Earlier another military spokesman, Yaroslav Chepurny, said the incident showed that Mariupol city remained under threat from separatists.
"The main danger (to Mariupol) - is in the further approach routes to the city - from the direction of Granitnoe, Starohnativka. We knew about this and were prepared," he said.
One Ukrainian servicemen was killed, one was missing in action and 16 were wounded in the past 24 hours, Lysenko said.
In Washington, U.S. State Department spokesman Joh Kirby said the United States was "deeply troubled" by the rise in attacks, which he said had left three Ukrainian soldiers dead and 35 wounded in the past several days.
Kirby said Ukraine had reported 127 attacks on Monday.
"Russia and the separatists it supports cannot simultaneously talk peace and fight," Kirby told a daily briefing. "If they want peace, they must implement the full ceasefire they agreed in Minsk."
He also condemned a weekend arson attack that destroyed four vehicles in Donesk belonging to OSCE monitors (Organization for Security and Cooperation in Europe).
More than 6,500 people have been killed since fighting between Ukrainian troops and rebels seeking independence from Kiev erupted in April 2014, according to U.N. estimates.
(Reporting by Alessandra Prentice, Natalia Zinets; additional reporting by Pavel Polityuk in Kiev and by Lesley Wroughton in Washington; Editing by Alison Williams and David Gregorio)