WASHINGTON (TIP)The FBI is investigating a suspected Russian cyber attack on a number of American banks. Hackers are believed to have targeted JP Morgan and at least four other banks in the US, amid increasing concern over cyber security from watchdogs on both sides of the Atlantic. The attack on JP Morgan reportedly resulted in the loss of “gigabytes of sensitive data” that could have involved customer and employee information. It is said to have been of a level of sophistication beyond ordinary criminals, leading to speculation of a state link.

The FBI is thought to be investigating whether there is a connection to Russia. American-Russian relations continue to be fraught amid the crisis in Ukraine, with sanctions ramped up. The bank is understood to have been in touch with executives in London to see if there is any link to its UK operations, but so far the attack, which happened earlier this month, is thought to have affected only the US. But watchdogs are increasingly worried about the city’s potential vulnerability to an aggressive state-backed hack.

A spokesman for JP Morgan said: “Companies of our size unfortunately experience cyber attacks nearly every day. We have multiple layers of defence to counteract any threats and constantly monitor fraud levels.” JP faced criticism in April when it blocked a payment from a Russian embassy to the affiliate of an American-sanctioned bank. Russia’s foreign ministry described the move as “absolutely unacceptable, illegal and absurd”.