As on other social networking sites, users can create personal profiles and make contact with other members. It already has more than 13,000 registered users -- the oldest is 87.
The free site includes forums on subjects including gardening, health, money and relationship advice as well as blogs by writers who share their lives and interests online. Linda Franklin writes a dating blog, Marianne keeps a light-hearted carer's diary called 'Keeping Mum', keen gardener Terry Walton writes 'Allotment Sagas' and Lucy Irvine’s 'Balkan Castaway' describes her new life in Bulgaria.
Andrew Goodsell, group chief executive of Saga, said: "The internet is a place where the over-50s are thriving. Saga Zone is a place where they can mingle and chat about issues important to them, be they amusing or serious."
Saga Zone is not alone in the social networking market for older people. In the US the site Eons launched last year with a focus on the baby boomer generation. Yet despite raising £16m from investors Eons has struggled and had to lay off a third of its staff last month, according to reports.
Nick Burcher, board member at Zed Media, said Saga's entry into the UK social networking arena was an effective way of connecting with its audience, which was increasingly willing to interact and form communities online, as evidenced by the popularity of Friends Reunited with older users.
Burcher said: "Over the last year there have been a number of moves into this area to tap into the older market online. Saga Zone is part of the company’s overall engagement and interaction with its customers, rather than a standalone social networking site for over 50s."
Burcher said that it was unlikely that older users of social network sites would devote the amount of time typical among younger users: "We are not seeing massive usage in these demographics in social networking. However, older users tend to be more loyal and less likely to jump on the next bandwagon, so they are more likely to be sticky and develop loyalty to one site over time.
"Social networking has been dominated by youth-oriented sites such as MySpace, Facebook and Bebo. MySpace is almost deliberately designed to alienate older users and preserve its exclusively young user base."
Making money from social networking was still a challenge faced by even popular sites, Burcher said: "Facebook is still wrestling with how to monetise their traffic, despite their massive user base."
A survey this year by Ofcom found that older surfers account for nearly a third of all time spent online by British web users, and are much more likely to spend money online. Nearly three quarters of respondents had bought flights and books online, and two thirds had bought electrical goods.