O2, T-Mobile and Virgin Mobile are reportedly on the verge of introducing advertising to their mobile video and internet portals.

According to New Media Age, the three mobile giants are set to follow rival operators Orange and 3 in announcing plans to allow advertising on their next-generation mobile platforms.

This week saw 3 unveil its upcoming ad-funded video content service, which allows visitors to its Planet 3 portal to access free ad-funded video content including news, comedy and film.

The portal will also continue to offer ad-free premium services such as full music videos and mobile games.

3's ad content, developed in partnership with Rhythm New Media, will be targeted to fit users' demographic data such as age and gender. Microsoft and Unilever have signed to advertise on the service when it launches in April.

Meanwhile, Nokia has launched two mobile advertising services. Nokia Ad Service, a fully managed service for advertisers to conduct targeted advertising on mobile platforms, was launched in Europe this week and will launch globally in the second half of the year.

Nokia Advertising Connector, aimed at operators wishing to explore targeted advertising, is due for commercial release by the end of 2007.

Tom Henriksson, director of Nokia Ad Service, said: "As advertisers struggle with targeting in traditional media such as print and TV, mobile advertising is becoming an increasingly attractive channel for brands."

Nokia has completed several pilot campaigns, and reports positive feedback from advertisers and mobile operators.

Mobile marketing and advertising in Europe and the US is forecast to exceed $1bn by 2009, according to analysts at MobileIN.com Research.