Twitter has been hit by a second distributed denial of service (DDoS) attack in less than a week.
The attack downed the microblogging site for just over half an hour yesterday, compared the three-hour outage cause by last week's attack.
It is not clear if yesterday's attack was related to the first attack, which is believed to have been aimed at a Georgian activist.
Other social media services, like Facebook and LiveJournal, were also affected by the attack.
At around 8pm UK time yesterday, Twitter said it was "working to recover from a site outage" and half an hour later said, "We're back up and analyzing the traffic data to determine the nature of this attack," in a status update.
The attack was confirmed as a DDoS attack in a blog posting by Alex Payne, Twitter's platform lead.
"We're currently experiencing another wave of Distributed Denial of Service (DDoS) attacks against our system," he wrote.
Despite the high-volume of last week's DDoS attack, investigators admitted that there is little evidence to identify the attackers or their location.
Twitter claimed no data or personal information was compromised in the attack, but said it was committed to improving system responses to assaults to prevent interruptions to the service.