The agreement allows O2 users to receive an SMS notification from Twitter when they are mentioned, or when they receive direct messages or when tweets are published by chosen friends.
"We believe that mobile will soon become the most popular way of accessing social networking sites, giving real-time access to tweets and status updates wherever you are," said Antony Douglas, head of content at O2.
"The agreements we now have in place with Twitter and the other key sites brings this a step closer, making it quick and easy for O2 customers to access their favourite social networks straight from their mobile."
The news could be particularly useful for companies using the micro-blogging service to keep track of their brand. However, O2 has warned that the free notification service is subject to an excessive use policy, and subscribers will be asked to moderate their use of the service if they exceed 600 messages per month.
Users can already send tweets by text, and will now have the option of replying by text. These messages are deducted from the subscriber's allocated SMS bundle or charged at the standard network rate.
O2 has existing agreements with Facebook and Bebo, and is developing a framework for the services to be rolled to other operations around the world via its Telefónica parent company.
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