BARI, Italy (Reuters) - Group of Seven financial chiefs said they had no idea who was behind the international cyber attack that affected almost 100 countries on Friday but they pledged to redouble their efforts to make cyberspace more secure.

The economy minister and central bank governor of Italy, which holds the G7 presidency, both replied negatively when asked at the end of a G7 meeting in Bari whether the group had any suspicions on the culprits of the attack.

“Frankly no, we discussed it but we don’t know anything,” Bank of Italy chief Ignazio Visco said.

However, the G7 promised to step up their work to try to prevent repetitions of the assault which leveraged hacking tools believed to have been developed by the U.S. National Security Agency, infecting tens of thousands of computers.

“This is a reminder to all of us of the importance and focus on cyber security,” said U.S. Treasury Secretary Steven Mnuchin.

“We had this on the agenda today, we were speaking about it, I think people felt so strongly about it that we agreed to keep it on the agenda for the next few sessions.”

The G7 said banks should strengthen their resilience to attacks through regular exercises and simulations, known as “penetration tests,” and it called on a cyber security task force it set up in 2015 to accelerate its work.

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“We recognize that cyber incidents represent a growing threat for our economies and that appropriate economy-wide policy responses are needed,” the G7 said in a statement.

It asked international organizations, government agencies and the private sector to share cyber security information more effectively and told its Cyber Expert Group (CEG) to draw up a set of recommendations by October this year.

Mnuchin told reporters that he did not think Friday’s attack showed the financial system was unprepared but he said more could still be done at the company level.

Companies that “patch their networks” would have been able to fend off the attack, he said.