Hackers attacked servers used by News International to publish some of its digital content at 2am on Thursday morning, apparently in retaliation for coverage in the Sun of the activities of the LulzSec hacking collective.

A senior source within News International confirmed to the Guardian that third-party architecture was affected for a couple of hours by a distributed denial of service (DDoS) attack, in which hundreds or thousands of machines make repetitive demands on an internet server.

The computers used for the attack were mainly based in Russia, but that does not mean that the people behind it were based there.

However, the attack did not delay the publication of the newspaper, and only caused delay in some of the digital publication, the source said.

"We haven't linked it to any particular coverage … the infrastructure that was affected isn't linked to The Sun."

Newspaper groups are on high alert at the moment for DDoS attacks from hacker groups as the issue has risen to prominence following the arrest on Tuesday of a man in Essex who has been charged with offences relating to attacks on websites.

Some hackers take offence at what they see as biased coverage.

No group appears to have claimed responsibility for this latest attack.