The crisis at Sony deepened on Tuesday as it admitted that an extra 25 million customers who played games on its Sony Online Entertainment (SOE) PC games network have had their personal details stolen – and that they were taken before the theft of 77 million peoples' details on the PlayStation Network (PSN).

The electronics giant said the names, addresses, emails, birth dates, phone numbers and other information from PC games customers were stolen from its servers as well as an "outdated database" from 2007 which contained details of around 23,400 people outside the US. That includes 10,700 direct debit records for customers in Austria, Germany, the Netherlands and Spain, Sony said.

The dataset was stolen on 16 and 17 April, before the PSN break-in, which occurred from 17 to 19 April. Sony said that it had not previously thought that the data was copied by the hackers who broke into its systems.

A Sony spokeswoman in Tokyo admitted that the company was unable to predict where or how or when the next attack would come. "They are hackers. We don't know where they're going to attack next," she said.

Another Sony spokeswoman said there was no evidence that the information taken had yet been used illicitly for financial gain. "We had previously believed that SOE customer data had not been obtained in the cyber-attacks on the company, but on May 1 we concluded that SOE account information may have been stolen and we are notifying you as soon as possible," Sony said in a message to customers. The company denied on its official blog on Monday rumours claiming that the hackers who stole the PSN details had tried to sell back 2.2m credit card details.

Though the latest credit card numbers did not include the CVV – the three-digit code used to verify credit card transactions – the hackers will almost surely be able to use the card details.

The latest news will be a serious blow to Sony's management, already reeling from the enormous revelation of the problems with the PSN, which has been offline for more than a week. Though there have been no reports of management changes, it is expected that there will be serious ramifications from the security breaches inside the company.

The SOE network hosts games that are played over the internet on PCs, and is separate from the PSN, which connects PlayStations online.

The SOE network was taken down on Monday and Sony suspended its SOE games on Facebook because they use "microtransactions" and the sale of virtual goods, if subverted could be used by hackers to make illicit transactions.

The company said it will grant players 30 days of additional time on their subscriptions, along with one day for each day the system is down.

It is also working with the FBI and other authorities to investigate what it called "a criminal cyber attack" on its data centre in San Diego, California.

The revelation comes after Sony No. 2 Kazuo Hirai announced measures had been put in place to avert another cyberattack like that which hit its PlayStation Network, hoping to repair its tarnished image and reassure customers who might be pondering a shift to Microsoft's Xbox.

The PSN incident has already sparked legal action and investigations by authorities in North America and Europe, home to almost 90% of the users of the network, which enables gamers to download software and compete with other members.

On Monday, Sony declined to testify in person in front of a US congressional hearing, but agreed to respond to questions on how consumer private data is protected by businesses in a letter on Tuesday, said a spokesman for Mary Bono Mack, a Republican Congresswoman from California, who is leading the hearing.

Sony denied on its official PlayStation blog on Monday that hackers had tried to sell it a list of millions of credit card numbers.