Russia warned Britain today that if British weapons were used by Ukraine to strike Russian territory then Moscow could retaliate by hitting British military installations and equipment both inside Ukraine and elsewhere.

Britain’s ambassador Nigel Casey was summoned to the Foreign Office to be served with a formal protest after Foreign Secretary David Cameron said last week that Ukraine had the right to use British weapons to hit Russia.

Russia’s foreign ministry said Cameron’s remarks acknowledged Britain was now de facto involved in the conflict, contradicting assurances that the long-range weapons it has given Ukraine would not be used against Russia.

“Casey was warned that in response to Ukrainian attacks on Russian territory with British weapons, any British military facilities and equipment on Ukrainian soil and abroad” could be targeted, the Foreign Office stressed.

The Russian ministry points out that it considers Cameron’s statements a serious escalation.

“The ambassador was called upon to contemplate the inevitably disastrous consequences of such hostile actions from London and immediately refute the aggressively provocative statements by the head of the Foreign Office in the most decisive and unequivocal manner.”

David Cameron, during a visit to Kiev last week, told Reuters that Ukraine has the right to use British-supplied weapons to hit targets inside Russia and that it is up to Kiev whether it does so or not.

Reuters has not been able to reach British officials for comment.