The Prime Minister has attended a top-level intelligence meeting in London to discuss growing international tensions with Russia.
The meeting of countries belonging to the Five Eyes network was a late addition to Jacinda Ardern's European tour.
She sat down with her British, Australian and Canadian counterparts amid accusations of Russian interference on millions of computers around the world.
The FBI in the US and GCHQ in the UK have warned against Russian attempts to hijack computers and internet routers around the world.
Ms Ardern has had a face-to-face with UK Prime Minister Theresa May at Downing Street, with the pair discussing trade and international tensions - including Syria and the Salisbury nerve agent attack.
Ms Ardern also met royals Prince Charles and Camilla, Duchess of Cornwall and London Mayor Sadiq Khan.