Moscow’s spies accused of breaking into American diplomats’ homes, killing a pet and paying for smear stories

John Kerry, the US secretary of state, has complained personally to Russia’s President Vladimir Putin over an officially sanctioned campaign of intimidation against US diplomats in Moscow, the US State Department has said.

The complaints follow two years of low-level harassment directed at US diplomats and their families that is believed to include frequent traffic police checks, following diplomatic staff around the city, and even breaking into their homes.