Houses of ParliamentImage copyrightPA
The UK Parliament has been hit by a cyber-security attack.
MPs were reportedly informed about the hack on Friday night and later told of difficulties in accessing their emails away from the Westminster estate.
A Commons spokeswoman said the lack of email access was not a result of the cyber-attack itself but part of the steps being taken to manage the issue.
She said Parliamentary authorities were liaising with the National Cyber Security Centre.
The spokeswoman said: "The Houses of Parliament have discovered unauthorised attempts to access parliamentary user accounts.
"We are continuing to investigate this incident and take further measures to secure the computer network..
'Disabled remote access'
"We have systems in place to protect member and staff accounts and are taking the necessary steps to protect our systems."
She added: "Parliament has disabled remote access to protect the network."
A number of MPs have confirmed to the BBC they are not able to access their parliamentary email accounts remotely.
It comes just over a month after 48 of England's NHS trusts were hit by a cyber-attack.
The latest attack was publicly revealed by Liberal Democrat peer Lord Rennard on Twitter who had also asked his followers to send any "urgent messages" to him by text.
Henry Smith, Tory MP for Crawley, later tweeted: "Sorry no parliamentary email access today - we're under cyber attack from Kim Jong Un, (Vladimir) Putin or a kid in his mom's basement or something..."
The government's National Security Strategy said in 2015 that the threat from cyber-attacks from both organised crime and foreign intelligence agencies was one of the "most significant risks to UK interests".
The National Cyber Security Centre, which is part of intelligence agency GCHQ, started its operations in October last year.
The National Crime Agency said it was working with the NCSC but the centre was "leading the operational response".