EU foreign policy chief Josep Borrell is due in Moscow on Friday just days after the jailing of prominent Russian dissident Alexei Navalny that provoked an international uproar.
Borrell has stressed he plans to call once again for Navalny's release during the trip, which includes meetings with Russian Foreign Minister Sergei Lavrov and with civil society figures.
But with calls growing for the European Union to hit Russia with fresh sanctions, a number of EU lawmakers have questioned the timing of Borrell's long-planned trip - the first such visit by such a high-ranking EU diplomat since 2017.
Borrell's trip comes before an EU foreign ministers meeting later this month where a joint reaction to developments in Russia is on the agenda. EU leaders are also due to discuss the matter at a March summit.
Sentenced to prison
A Moscow court sentenced Navalny to three and a half years in a penal camp for a probation violation.
The prominent anti-corruption campaigner failed to check in with authorities while in Germany recovering from a poison attack that has been blamed on Russian domestic intelligence.
The Kremlin has so far brushed off foreign criticism as external interference.
