Senior Obama strategist David Axelrod today offered something of a fireworks display on Twitter, launching a barrage of messages meant to draw attention to two reports that highlight Mitt Romney's stake in a Bermuda company that has never been listed on his state or federal financial reports.

@DavidAxelrod: Astonishing story about Mitt's Bermuda tax shelter and his efforts to keep it secret, apparently skirting MA law. 1/4

@DavidAxelrod: A Swiss bank account. A dozen funds in the Cayman Islands. And now, a Bermuda tax shelter he failed to report. 2/4

@DavidAxelrod: How many of these revelations will it take for the media to demand a full accounting of Mitt's tax returns and finances? 3/4

@DavidAxelrod: Or will his campaign continue to stonewall and keep him secure within the MPP-the Mittness Protection Program? 4/4

The company in question - Sankaty High Yield Asset Investors Ltd. - is described by government financial documents as "a Bermuda corporation wholly owned by W. Mitt Romney." Yet, as both Vanity Fair and the Associated Press note in new reports, it has never appeared on the candidate's financial disclosure forms. Limited details on its existence only recently came to light when Romney released his 2010 tax return under public pressure.

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"Even after examining that return, we have no idea what is in this company, but it could be valuable, meaning that it is possible Romney's wealth is even greater than previous estimates," writes Nicholas Shaxson in Vanity Fair. "While the Romneys' spokespeople insist that the couple has paid all the taxes required by law, investments in tax havens such as Bermuda raise many questions, because they are in 'jurisdictions where there is virtually no tax and virtually no compliance,' as one Miami-based offshore lawyer put it."

Notes AP's Stephen Braun, "The omissions were permitted by state and federal authorities overseeing Romney's ethics filings, and he has never been cited for failing to disclose information about his money. But Romney's limited disclosures deprive the public of an accurate depiction of his wealth and a clear understanding of how his assets are handled and taxed, according to experts in private equity, tax and campaign finance law."

Democrats say Romney's secretive financial holdings raise questions about his intentions and potential conflicts of interest. They say the Bermuda company - along with a Swiss bank account, Cayman Islands accounts, and other foreign funds, Romney has had ties to - suggest that Romney is "betting against America." It's a theme President Obama will push during his two-day, two-state bus tour which kicks off tomorrow in Ohio.

Romney spokeswoman Andrea Saul told AP the governor has complied with all state and federal laws. "Everything on the filings is reported as required. If OGE [Office of Government Ethics] has an issue with any filings, they would let us know," she said.

In a statement to ABC News, Romney spokeswoman Amanda Henneberg called Axelrod's tweets part of a pattern of allegations that "have been proven false time and again."

"As job growth slows, manufacturing activity stalls, and our economy continues to sputter, President Obama knows he can't make a legitimate argument for another term in office, so instead he is trying to tear down his opponent," she said. "This is just the latest example of President Obama and his political machine saying or doing anything to distract from his abysmal record over the last four years."