Cook said "the most personal device we have ever created" can display a variety of faces ranging from a classic watch face to an animated Mickey Mouse.

Watch: Apple takes leap into new territory with smartwatch

Connecting wirelessly to a user's iPhone, the watch is designed as a wrist device for messaging, calls and a variety of health apps.

An Apple statement described it as "an intimate and immediate communication device and a groundbreaking health and fitness companion."

Apple enters a market that already has a number of players, ranging from South Korean giants Samsung and LG, to Japan's Sony and startups such as Pebble.

But analysts expect Apple to lift the market by integrating the watch with the iPhone and its software ecosystem, and its range of apps and sensors for health and fitness.

"Competing smartwatch makers have to be breathing a sigh of relief; yet, Apple will outsell all the rest of them combined this year," said Forrester analyst James McQuivey.

"But in so doing, Apple will bring very valuable attention to the market, essentially releasing a rising tide that will float all their boats."

For communication, Apple Watch offers a range of apps and can be used as a sort of wrist-radio from the Dick Tracy comics.

"With the built in speaker and microphone you can receive calls on your watch. I have been wanting to do this since I was five years old," Cook said.

 Pay from the wrist 

The watch is integrated with Apple Pay's mobile wallet and can be used to view pictures, monitor news and connect to social media.

The watch can use other apps ranging from Uber ride-sharing to music to home automation.

"Now it's on your wrist, not in your pocket or your pocketbook," Cook said.

"I think you're going to be surprised at what developers can do when you unleash that community."

Apple demonstrated using the watch to listen to music, with lyrics displayed on the watch face.

The company also demonstrated an app to open a garage door from afar to let in a family member who is locked out.

But one of the keys will be the health and fitness applications.

The watch has an accelerometer, a heart rate sensor and sensors for "a comprehensive picture of your all-day activity and workouts."

It will prompt a user to get up and walk if sedentary too long.

All-day battery 

Cook boated that the device will have "all-day battery life" - or some 18 hours.

Entry price will be US$349 in the United States, with costs up to US$1,049 for extra features. A solid gold limited edition will be priced from US$10,000 to US$17,000.

Initially, it will be available in Australia, Canada, China, France, Germany, Hong Kong, Japan, Britain and the United States. Pre-orders will be taken from April 10.

Moor Insights and Strategy founder Patrick Moorhead, who attended the event, said "the secret weapon here is the ability to message each other by tapping on the watch, I think people, particularly kids, are going to go nuts over that.

"Apple has a big chance of success, and what that is going to do is set the bar for the experience that the entire smartwatch," he added.

Jan Dawson at Jackdaw Research said he expects Apple to sell around 20 million of the devices this year, and that this will "catalyse the overall smartwatch market and help other vendors even as Apple comes to enjoy levels of market share it hasn't had since the iPod."

Research firm Strategy Analytics predicts Apple will sell 15.4 million units worldwide this year, to give Apple a 55 per cent market share.

At the event, Apple also unveiled a new Macbook laptop computer than weighs less than one kilo (two pounds).

"We challenged ourselves to re-invent the notebook (computer), and we did it," Cook said.

The new MacBook starting at US$1,299 is 13.1 mm at its thickest point, and its features include all-day battery life; a high-resolution 12-inch edge-to-edge screen, and greatly-enhanced keyboard and trackpad.