Twitter Inc. shares fell by as much as 15% in pre-market trading July 27 as the company failed to increase its average monthly active user figures during its second quarter.

The social media giant's average monthly active users, or MAUs, fell by 1 million from the previous quarter to 335 million, while daily active users bumped up 11% year over year. Twitter expects MAUs to drop again in the third quarter, by "mid-single-digit millions."

Speaking on a same-day earnings call, CEO Jack Dorsey attributed the drop in monthly users to "improving the health of the public conversation" on the platform. He also cited the General Data Protection Regulation's sweeping privacy laws in the European Union that took effect in May.

The company suspended more than 70 million fake or suspicious accounts in May and June, and continued to shut down accounts at a clip in July, according to a report from The Washington Post. Twitter has more than doubled its rate of account suspensions since October 2017 when it told Congress that Russia used fake accounts to interfere in the U.S. presidential election.

"We believe that Twitter's value as a daily service is enhanced when the conversation on the platform is healthier and people feel safe freely expressing themselves," he said.

When Dorsey was asked about how much work is left to remove malicious accounts from the site, he said the company does not "think that this work will necessarily ever be done."

Twitter earlier on July 27 reported a 23.8% year-over-year gain in revenue for the second quarter to $710.5 million, up from $573.9 million in the prior-year period.

Net income was $100.1 million, or 13 cents per share, compared to a net loss of $116.5 million, or a loss of 16 cents per share, a year ago. Notably, the quarterly income includes $42 million net tax benefit primarily driven by the release of a valuation allowance for Brazil.