MediaNews and Hearst Corp., the Bay Area’s two biggest newspaper publishers, have announced a joint purchase of 80 percent of the online classified-advertising software provider Kaango for about $20 million, according to a filing with the Securities and Exchange Commission (See page 16).

In the past few months, the two publishing companies have become increasingly intertwined while still officially remaining competitors in the Bay Area in the eyes of federal antitrust regulators:

• On Oct. 23, Hearst paid $317 million for a 31 percent stake in MediaNews Group’s operations outside the Bay Area.

• On Oct. 25, Hearst bought two newspapers in Connecticut that MediaNews will manage.

• On Nov. 6, the Chicago Tribune reported that Hearst, MediaNews were talking about forming a national online advertising network with three other chains (Gannett, a MediaNews minority investor in MediaNews Group’s Bay Area papers; Tribune Co., owner of the Los Angeles Times, and Cox owner of KTVU Channel 2).