KYIV, Ukraine (AP) — Ukraine's President Volodymyr Zelenskyy has asked for a phone call with Russia’s President Vladimir Putin about the Russian troop buildup across his country's border and the escalating tensions in eastern Ukraine, but the request has been left unanswered so far, Zelenskyy's spokeswoman said Monday.

“The Kremlin, of course, has the request to talk to Vladimir Putin. We haven't received a response so far and very much hope that it's not a refusal of dialogue,” Iuliia Mendel told The Associated Press. The request was lodged on March 26, when four Ukrainian troops were killed in a mortar attack in the east, she added.

Kremlin spokesman Dmitry Peskov said Monday he hasn't seen any requests from Zelenskyy “in recent days” and is not aware of any such requests having arrived.

The exchange comes as tensions escalate in eastern Ukraine, where Russia-baked separatists and Ukrainian forces have been locked in a conflict since shortly after Moscow’s 2014 annexation of Ukraine’s Crimean Peninsula. More than 14,000 people have died, and efforts to negotiate a political settlement have stalled.

Western and Ukrainian officials have raised concerns in recent weeks about increasingly frequent cease-fire violations in the conflict area. Reports of Ukraine's military casualties have been occurring daily over the past week, and rebels also have reported losses. On Monday, Ukraine’s military reported one more serviceman killed, bringing the total to 28 since the beginning of the year.

The Russian troop build-up along the border with Ukraine has elicited concerns both in Ukraine and in the West. Zelenskyy is expected to head to Paris soon for talks on the Russian troop build-up and the escalation of tensions in the conflict area with French President Emmanuel Macron, Mendel said Monday.

She said that Russia has accumulated 41,000 troops at its border with eastern Ukraine and 42,000 more in Crimea. These numbers are likely to grow as the troops “keep arriving," she said.

The Kremlin has maintained that Russia is free to deploy its troops wherever it wants on its territory and has repeatedly accused the Ukrainian military of “provocative actions” along the line of control in the east that threatens Russia’s security.