(REUTERS) -- Shares of cruise operator Carnival Corp. plunged 15 percent on Tuesday after a ship operated by its unit struck a submerged rock and keeled over off the coast of Italy late on Friday.

At least three people died in the accident and dozens are still missing.

Shares of Carnival's rival Royal Caribbean Cruises were down 7 percent.

Susquehanna Financial cut its rating on both the stocks to neutral from positive due to the potential impact of the tragedy on the sector.

Carnival's shares touched a near three-month low of $29.23 in morning trading on the New York Stock Exchange and those of Royal Caribbean dropped to $26.75.

(Reporting by Chris Jonathan Peters in Bangalore; Editing by Maju Samuel)