Russia will soon expel British diplomats in retaliation for Britain's decision to expel 23 Russian diplomats over the poisoning of a former spy in southern England, Foreign Minister Sergei Lavrov said on Thursday.

"Absolutely. Soon," the RIA news agency cited Lavrov as saying, when asked if Moscow was ready to kick out British diplomats.

Lavrov said British allegations of Russian's involvement in the attack were unacceptable.