SAN FRANCISCO - FILE: Attendees mingle during a break at the first annual Chirp, Twitter Developer's Conference April 14, 2010 in San Francisco, California. (Justin Sullivan/GETTY IMAGES)

Twitter said Tuesday afternoon that it had resolved an issue that had prevented some users from logging in to the site for several hours earlier in the day.

Users were reporting problems using the service across the Web, due to what appeared to be a glitch with the site log-in. Those already logged in to Twitter appeared to be able to use the service, but some of those trying to log in were unable to access their accounts.

Twitter has been taking steps to improve its service and make it more secure for users.

The company recently introduced a new two-factor login service aimed at making it easier and hacker-safe for users to sign in to their accounts. Under the new system, users have the option to sign in to the company’s Web site using their username and password, and then have the service send a second, short code to the Twitter app on their phone for extra verification.

The feature is designed to make it more difficult for those intent on breaking into an account to gain access, since it requires the person logging in to have the account holder’s smartphone.

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