At 13.7 millimeters, the new Nokia N76 phone is as slender as most slim-line models from smaller rivals. The RAZR is 14 mm thick and lags far behind in terms of features.
Nokia plans to launch the new ultra-thin Barracuda phone later in the year, although it has not yet revealed the measurements of this offering.
Nokia has been able to hang on to a global market share of around 35 percent thanks to booming demand for its cheaper models in emerging markets.
Nokia introduced its powerful N-Series in 2005, soon after Motorola hit gold with its thin but not very powerful RAZR.
It launched a new version of its N93 -- the N93i -- that is 3 mm slimmer and doubles as a digital video camera. It will be available for 600 euros in the first quarter.
The N76 will be sold in the first quarter for around 390 euros ($511) before taxes and subsidies from operators.
The Finnish company also unveiled a new Internet tablet using the Linux operating system. Building on Nokia's first tablet -- the 770 -- the N800 is faster, has a full-screen finger QWERTY keyboard and an integrated Web camera.
The device, which avoids time-consuming network-approval steps from mobile operators through a Wi-Fi short-range wireless Internet connection, will be available immediately in the United States and several European markets for around $400 and 400 euros respectively.
Nokia also will work with EBay's Skype to add Skype calls to the tablet by the end of the first half of 2007.