The suits accuse the hotels of using the fees as a way to increase revenue without appearing to raise their room rates. Resort fee notices often are hidden in “obscure” areas, appear in smaller print, or under misleading headings suggesting they are fees imposed by local governments, the suits said.

The lawsuits seek to force the chains to advertise the true prices of their hotel rooms up front, pay money to consumers who were harmed by the fees and pay civil penalties.

At least 79 Hilton properties in the United States charge the fees, the Nebraska complaint said.

“Resort fees are charged at less than 2 percent of our properties globally, enable additional value for our guests, and are always fully disclosed when booking” on Hilton’s website or mobile app, Nigel Glennie, a Hilton spokesman, said in an emailed statement. He declined to comment on fee disclosures on third-party travel sites. Hilton has about 6,000 properties worldwide under various brands.

A Marriott spokesman said in an email that the company did not comment on litigation, “but we look forward to continuing our discussions with other state A.G.s.” He did not respond to a question about the status of those talks.

Marriott oversees some 7,000 hotels under more than two dozen brands.

The resort fees — sometimes called amenity or destination fees — vary by hotel. Fees range from $9 to $95 per day at Marriott, and $15 to $45 a night at Hilton hotels, the suits said.

The American Hotel & Lodging Association, an industry group, maintains that resort fees are “not widespread,” according to its website.

But the fees have been an issue for years. In 2012 and 2013, the Federal Trade Commission warned more than two dozen hotels and travel booking websites that their pricing practices around resort fees may violate consumer protection laws by misrepresenting the true price of hotel rooms.