A number of BBC Twitter accounts were hacked by a group identifying itself as the Syrian Electronic Army.
A string of messages about bogus weather conditions in the Middle East appeared on the weather feed.
A BBC spokeswoman said: "We apologise to our audiences that this unacceptable material appeared under the BBC's name."
A phishing email was also sent to some BBC email accounts, although it has not yet been established if the two are connected.
The email included a link which, if followed, could have exposed password details.
The Syrian Electronic Army has previously spread messages supporting Syrian President Bashar-al-Assad.
Faris Couri, BBC Arabic's editor-in-chief said: "BBC Arabic's twitter account @BBCArabicOnline was hacked. Since then, several pro-Assad news tweets were published by the account.
"We strongly condemn such action and apologise to our audiences," he said.
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