Use of the internet-based messaging service Twitter is soaring, particularly from smartphones, according to new surveys and company executives.
Both the number of users and their tweets of 140-word character updates has been rising sharply, driven by news such as Osama bin Laden's death, big events including the UEFA Champions' League football final and interest in celebrities.
A poll released on Wednesday by Pew Research Centre found that twice as many American internet users aged 25 to 44 were on the service in May as opposed to six months earlier, with 13 percent of connected US adults now on Twitter versus 8 percent in November.
Pew found that half of US Twitter users get on to the service from a mobile device.
But Twitter chief executive Dick Costolo said even that growth was vastly understated, adding that third parties hadn't been able to measure the total usage because of the variety of software interfaces and devices employed to communicate through Twitter.
"What we see internally is that we are growing much faster than that," Mr Costolo said at a Dow Jones technology conference outside Los Angeles.
"We have grown our mobile usage over 150 percent since the beginning of the year." While Mr Costolo declined to say whether Twitter was profitable and demurred on when it might seek a public stock sale, he unveiled improvements to the site at the conference and said the introduction of advertising last year had already produced "unbelievable" results for marketing campaigns.
In the next few weeks, he said, Twitter would roll out new functions making sharing photos and videos nearly as easy as sending the 140-character texts and shortened web links that are the most common use of the service.
The topic-search function will also change so that it ranks tweet messages by relevance instead of simply in reverse chronological order. The results will be ordered based on factors including how many followers a user has, and will also include the most popular photos and videos associated with the topic.
The number of advertisers on the site, meanwhile, has gone from 150 at the end of last year to more than 600 now, with rates of engagement approaching those for Google's AdSense.
A sponsored "trending topic" from Volkswagen led 52 percent of those who saw it to click through, comment or retweet it, Mr Costolo said.
Though Pew records internet users' perceptions of their own behaviour, the indication of a fresh acceleration in Twitter's growth was echoed by research house Comscore, which estimated a 47 percent increase in unique visitors to Twitter's website in the year to April, to 123 million people globally.
Mr Costolo cited a far higher internal figure, some 350 million unique users per month.
Analysts believe that 300 million people have signed up to use Twitter since its creation in 2006, although the company will confirm only that it has "more than 200 million registered accounts".
Aaron Smith, analyst at Pew, said: "It is a tool that has a low barrier to entry - it's amenable to using on your mobile device and it doesn't require you to register if you want to dip your toe in the stream." The volume of information posted on the site also continues to grow, with about 1bn tweets every six days.
Last week during the Champions' League soccer final between Manchester United and Barcelona, Twitter reached its second highest spike at 6,303 tweets per second, more than double the record set during the football World Cup last summer but behind the peak of more than 7,000 during the New Year's celebrations in Japan.
In the UK, wider public interest in Twitter has been piqued by several accounts that have broken press gagging orders brought by celebrities in an attempt to protect their private life.
According to Experian Hitwise, UK traffic to Twitter hit an all-time high during last week's "super-injunction" debate, accounting for one in every 184 visits to a website on May 21.