NTT DoCoMo has invested $3 million in US Linux developer MontaVista.

The investment is part of the company's - Japan's biggest mobile phone carrier - plans to assist Japanese handset vendors develop more models that use the Linux OS, said spokeswoman Tomoko Tsuda. "The investment will help us have a direct relationship with MontaVista so they can help mobile phone makers get products to the market faster," she said.

MontaVista, based in California, provides an open source Linux-based operating system platform that can be used in electronic devices. DoCoMo is encouraging vendors to adopt either Linux or the Symbian OS on the new 3G phones that they make for the carrier and some have already done so.

In November, two of Japan's major handset vendors, NEC and Panasonic, released 3G models that use MontaVista's Linux OS. Both companies said they intend to release more Linux OS-based models.

Among other Japanese vendors, Fujitsu is a major supporter of Symbian and has released a number of models using Symbian OS.

NTT DoCoMo has developed a common software platform that can run on both Linux and Symbian OS. The platform consists of middleware, customised modules for the operating systems, sample device drivers, sample application software, handset emulator software for personal computers, and development guidelines.