By Gabriela Baczynska

KYIV (Reuters) – Germany’s Lufthansa has rescheduled at least two flights to Ukraine this week, in one of the first changes to air traffic since the latest step-up in tensions between Russia and the West.

A Lufthansa flight from Frankfurt to Kyiv on Sunday afternoon was moved to Monday morning, with Lufthansa service centre staff saying this was because crew could no longer stay in Kyiv overnight due to the current “problems”, a Reuters reporter who witnessed the announcement said.

Tensions have escalated after Russia massed an estimated 100,000 troops within reach of the Ukrainian border, although Moscow denies any intention of invading. [L8N2U41TF]

Several countries have issued warnings over the risk of flying near Ukraine’s eastern border region, some 450-550 miles south-east of Kyiv, since Malaysian Airlines flight MH17 was shot down in 2014, killing all 298 people on board.

The U.S. Federal Aviation Administration recently renewed a ban on U.S. airlines flying over parts of eastern Ukraine.

Canada warned last week of “heightened military activity” and the “threat posed by miscalculation and miscommunication”.

Lufthansa’s Frankfurt-Kyiv flight scheduled for Monday afternoon was moved to Tuesday morning, Frankfurt airport’s online departure board showed, while no such flight featured on Wednesday.

“We have adjusted our flight schedule to Ukraine for operational reasons only,” a Lufthansa spokesperson said on Monday, while another confirmed there would be no layovers in Kyiv for the time being.

Both did not comment further on the situation.

The Frankfurt airport website showed a 10:10 pm Lufthansa flight on Monday to the Ukrainian city of Lviv, which is about 330 miles (540 km) west of Kyiv, was due to go ahead. Lufthansa serves Kyiv, Lviv and Odessa in Ukraine.

Russia annexed the Black Sea peninsula of Crimea from Ukraine in 2014 and has sided with rebels fighting government troops in Ukraine’s eastern region of Donbas, where the Ukrainian government says some 14,000 people have been killed.

The European Union has threatened Moscow with sanctions if it invades Ukraine again, the United States provided Kyiv with more arms and NATO said it was putting forces on standby.

Russia has denounced the moves as an escalation of tensions. It has demanded that Washington guarantees Ukraine will never join the Western military alliance.

(Reporting by Gabriela Baczynska; Additional reporting by Allison Lampert; Editing by Tim Hepher and Alexander Smith)