A newly discovered piece of destructive software found circulating in Ukraine has hit hundreds of computers, according to researchers at the cybersecurity firm ESET, part of what Ukrainian officials said was an intensifying wave of hacks aimed at the country.

In a series of statements posted to Twitter, the company said that the data wiping programme had been "installed on hundreds of machines in the country," an attack it said had likely been in the works for the past couple of months.

Vikram Thakur of cybersecurity firm Symantec, which is also looking into the attacks, told Reuters that...