A Dutch diplomat has been attacked in his Moscow apartment by two unidentified men following the arrest of a Russian diplomat in the Netherlands that caused outrage.
The incidents involving the Russian and Dutch diplomats come at a time of growing tensions between the two countries over Russia's seizure of a Dutch-flagged Greenpeace ship and Russia's anti-gay laws.
Russia's Investigative Committee said it was investigating the attack on the diplomat, who it said was pushed to the floor and tied up with tape.
Dutch foreign minister Frans Timmermans said the diplomat was slightly injured in the assault on Tuesday night. Mr Timmermans said he had summoned the Russian ambassador for an explanation. "Our people have to be able to work safely and I want guarantees that the Russian authorities will accept their responsibilities on that point," he said.
Russia was angered by the arrest of its diplomat Dmitry Borodin in The Hague earlier this month after police had traced a car involved in an accident to his home, and neighbours told them they were worried for the safety of children inside.
Relations were already tested by Russia's seizure last month of the Greenpeace ship, which was protesting at oil drilling in the Arctic. Russia has charged all 30 people on board with piracy, which carries a maximum 15-year sentence.
The Netherlands and Russia chose 2013 as a year to celebrate historical ties, but it has been filled with tension instead.
The Russian Foreign Ministry said the Dutch diplomat was Onno Elderenbosch, the deputy chief of mission at the Moscow embassy - the same rank as Mr Borodin holds at the Russian embassy in the Netherlands.
"In Moscow we express our regrets in connection with the deplorable incident," a foreign ministry spokesman said.