Twitter is investigating how it’s own chief executive Jack Dorsey’s official account was hacked, with racist and vulgar tweets sent to his 4.2 million followers.

Some of the tweets were up for about 30 minutes on Friday before Twitter took them down.

The tweets included messages such as “Hitler is innocent” and, using a vulgarity, asked “bald skeleton head”, referring to Mr Dorsey, to unsuspend certain accounts.

Mr Dorsey is the founder and CEO of the Twitter microblogging site as well as the co-founder of the electronic payment company Square.

Twitter’s communications team posted there was “no indication” their systems had been compromised.

And by 8pm on Friday local time, a second message from Twitter HQ in San Francisco explained the “security oversight” was by the mobile provider.

The phone number associated with the account was compromised due to a security oversight by the mobile provider. This allowed an unauthorized person to compose and send tweets via text message from the phone number. That issue is now resolved.

— Twitter Comms (@TwitterComms) August 31, 2019

The company suspended accounts that the hacker or hackers retweeted while they had control of Dorsey’s account.

The incident comes as Twitter and Mr Dorsey promised to improve the “health” and civility of discourse on the social media service, cracking down on hate speech and abuse.