The Kremlin on Tuesday warned it would respond if the European Union makes it harder for Russians to travel to the bloc as part of measures in support of Ukraine.
The idea to ban Russian tourists from Europe has divided EU nations, with some in full support and others fearing it would shut the door on dissident Russians fleeing abroad.
EU foreign ministers will discuss the issue during a two-day meeting in Prague that starts Tuesday.
"We know that there are different views among Europeans on the matter. We will follow this closely. This is a very serious decision that could be directed against our citizens," Kremlin spokesman Dmitry Peskov told reporters.
"Of course, such decisions cannot remain without an answer," he said.
"Step by step, Brussels and individual European capitals demonstrate an absolute lack of reason... This mix of irrationality, bordering on the insane, allows for such decisions (on visas) to be discussed," Peskov added.
Brussels has imposed a slew of unprecedented sanctions on Moscow in response to Russia's attack on pro-Western Ukraine that began in late February.
The EU had already suspended visa facilitation for Russian official delegations and business leaders, but short stay visitors are allowed to travel to the bloc.
Although Ukraine has called for Russian tourists to be banned completely from the EU, a symbolic suspension of a deal that facilitates visa applications is expected.
Russian leisure travellers use Schengen visas normally valid across 26 EU and associated countries, including Switzerland and Norway.
The visas typically allow stays of up to 90 days in a 180-day rolling period.