Pietersen apologised for his online outburst
Batsman Kevin Pietersen has been fined an undisclosed sum for a Twitter tirade which followed a decision to drop him from England's one-day team.
He used an expletive in an angry message in response to being omitted from the squad for the Twenty20 and 50-over series against Pakistan.
The 30-year-old attended a disciplinary hearing at Lord's on Monday and pleaded guilty to two charges.
He also offered an "unreserved apology" to the England management team.
"The hearing considered his comments to be prejudicial to the interests of Team England and the England and Wales Cricket Board and a significant breach of the England player conditions of employment," read an England and Wales Cricket Board statement.
Pietersen's tweet, which appeared briefly prior to the offical announcement of England's squad on 31 August, was intended for friends and he hastily deleted it after realising his mistake.
"It wasn't meant for the public domain," he said the following day.
Pietersen was one of the stars of England's triumph at the World Twenty20 tournament in the Caribbean earlier this year, but the selectors decided to give him a break from the international game after he admitted his confidence was low following the recent Tests against Pakistan.
Since then, he has returned to county cricket with Surrey and hit 116 off 105 balls in a 40-over match against Sussex last weekend, his first century for 18 months.
He is not the first player to fall foul of the game's authorities because of messages on Twitter.
Last October, England team-mate Tim Bresnan was warned about his future conduct after swearing in a tweet and earlier this summer, Yorkshire's former England Under-19s captain Azeem Rafiq received a one-month ban for a similar offence.
The Rafiq case prompted England captain Andrew Strauss to issue a warning to "be careful" when using social network sites.
He added: "Players should be aware that what they write is going to be seen by people they might not want it to be seen by."
England bowler Stuart Broad also sounded a similar warning on Monday. "Some people really enjoy it, some players aren't involved. I've not gone on it," he told BBC Sport.
"It's up to every player to be aware of the responsibility of their actions, and it's up to the ECB to govern that. People need to be aware that you are putting yourself out there and you have to be responsible about your actions."
Meanwhile, Hampshire's Dimitri Mascarenhas has been fined £1,000 by his county after a Twitter rant at England chairman of selectors Geoff Miller.
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