Apple is experiencing problems with its iTunes Store and iCloud services, with many Twitter users reporting that they are unable to log in using their Apple ID to download apps.

On Twitter, users in a number of countries were confirming the problems. When trying to login on Friday morning Central European Time (CET) they were greeted with "The Apple ID you entered couldn't be found or your password was incorrect. Please try again"

The error doesn't affect all users: Around 11 a.m. CET an IDG News Service reporter in London was able to log in using his iPhone, although a colleague in Paris wasn't. The French user was able to log in again around 11.40 a.m. after accepting new terms and conditions for the iTunes store.

Users trying to change their password were also greeted with an error message, according to Twitter messages.

Apple had no comment, according to a spokesman.

The iCloud system status page says all services are online -- but it has not been updated since 6.30 p.m. PST on Dec. 5.

Apple's app stores have been a key factor in the success it has seen in the last couple of years. Earlier this week, the company boasted that it had distributed more than 100 million programs through the Mac App Store since its January launch.