Yahoo on Thursday launched a web-based version of its free instant messaging service for Internet users who want to stay connected while away from their home computers. Yahoo Messenger for the Web lets people use the online search titan's service from any Internet-linked computer without needing to download or install software, as was the case previously.

The service is tailored for use by travelers, workers whose employers block software downloads to company machines, cyber-cafe dwellers and people who simply cannot afford their own computers.

The new service is introduced as Yahoo vies with rivals Google and Microsoft for the devotion of Internet users whose visits can be parlayed into online advertising revenue.

Users of Yahoo's instant messaging system can engage in exchanges with people using Microsoft's Windows Live Messenger.

Yahoo Messenger for the Web is available online at http://webmessenger.yahoo.com.

The service is initially launching in Brazil, India, Malaysia, Philippines, Vietnam and the United States. It is to be made available in other countries through the rest of the year.