Nov 14 (Reuters) - SpaceX has bought an advertising package on Twitter for its satellite internet service Starlink, said Elon Musk, who owns both the rocket company and the social media platform that has seen an exodus of advertisers.

"SpaceX Starlink bought a tiny – not large – ad package to test effectiveness of Twitter advertising in Australia & Spain. Did same for FB/Insta/Google," Musk tweeted on Monday.

Twitter, which generated more than 90% of its second-quarter revenue from ad sales, has seen advertisers flee on fears that Musk would change the company's content-moderation rules.

Companies including General Motors Co, General Mills , Mondelez International and Volkswagen AG paused advertising on the platform after Musk acquired it last month.

"At the moment most clients are suspending their activities (on Twitter) because they're worried about extreme content and content moderation on the site," S4 Capital's Martin Sorrell said on Monday.

Sorrell added that it "doesn't pay to bet against" Musk and that he would "get it right in the end."

The chief executive of Tesla Inc and SpaceX had last week told advertisers that he aimed to turn the social media platform to pursue truth and put an end to fake accounts.

He also raised the possibility of Twitter going bankrupt days after disclosing that the platform had seen a "massive" drop in revenue and blamed activist groups pressuring advertisers.

Tesla shares fell about 2% in premarket trading after Musk said, "I have too much work on my plate that is for sure," when asked about his leadership at the EV maker and Twitter.

A Platformer reporter on Monday said Twitter has locked down its code base, freezing any production changes to its systems until further notice, citing an internal email.

That means engineers can add no new features, nor can they make changes to the existing Twitter experience. Exceptions will be made only if Musk says so explicitly, the tweet said. (Reporting by Akriti Sharma and Akash Sriram in Bengaluru; Additional reporting by Chavi Mehta; Editing by Vinay Dwivedi and Arun Koyyur)