Tim Cook is pretty pleased by sales of the Apple Watch this holiday shopping season.

The Apple CEO told Reuters the gadget set a sales record during the first week of holiday shopping and is on track for its best quarter yet.

"Our data shows that Apple Watch is doing great and looks to be one of the most popular holiday gifts this year," Cook wrote Monday in response to an email from the news agency. Cook went on to say that the Apple Watch reached a new high on sell-through, which measures the number of units actually sold to consumers compared with the quantity distributed to retailers.

"Sales growth is off the charts. In fact, during the first week of holiday shopping, our sell-through of Apple Watch was greater than any week in the product's history. And as we expected, we're on track for the best quarter ever for Apple Watch," he said.

Apple unveiled the second generation of its Apple Watch in September. The device, which starts at $369 (£369, AU$529), looks identical to the first model but comes with one notable improvement: It's waterproof enough for swimmers.

The company doesn't report sales data for its Apple Watch, the first new product released under the leadership of Cook, who needs to show that the company can still create lust-worthy, must-have products in new categories.

Cook's comments come as technology research firm IDC reported that Apple shipped 1.1 million units of the Apple Watch in the three-month period ended in September, a decline of 71 percent from the same quarter a year ago.

Apple did not immediately respond to a request for more specific sales figures.