Tesla Inc. and its chief executive, Elon Musk, were sued twice on Friday by investors who said they fraudulently engineered a scheme to squeeze short-sellers, including through Musk's proposal to take the electric-car company private.

The lawsuits were filed three days after Musk stunned investors by announcing on Twitter that he might take Tesla private in a record $72 billion transaction that valued the company at $420 per share, and that "funding" had been "secured."

In one of the lawsuits, the plaintiff Kalman Isaacs said Musk's tweets were false and misleading, and together with Tesla's failure to correct them amounted to a "nuclear attack" designed to "completely decimate" short-sellers.