The U.S. Department of State on Monday advised U.S. citizens currently in Russia to consider departing the country "immediately," citing Moscow's ongoing military actions in Ukraine and what the department expected to be potential "harassment" toward Americans by "Russian government security officials."

The State Department said in an updated travel advisory that the U.S. government's ability to assist Russia-based U.S. nationals is "limited" now, so Americans should consider leaving the country "via commercial options still available."

The European Union closed its airspace to Russian aircraft on Sunday, three days after the U.S. Federal Aviation Administration expanded a "no-fly zone" to cover the entire territories of Ukraine and Belarus, as well as the western part of Russia. An increasing number of airlines are cancelling flights into and out of Russia.

As such and given "the ongoing armed conflict," the State Department in its advisory advised U.S. citizens against traveling by land from Russia to Ukraine, and urged those near the Russia-Ukraine border and those who plan to travel there "to be aware that the situation along the border is dangerous and unpredictable."

Ukrainian and Russian delegations concluded the peace talks at the Ukrainian-Belarusian border on Monday, with the next round of negotiations scheduled for the coming days on the Belarusian-Polish border, according to the Russian delegation.