Advertising stocks are likely to be among the worst hit when the New York Stock Exchange opens later today.

Interpublic, the world's biggest advertising group and owner of global ad agencies including McCann-Erickson and Lowe Lintas, and Omnicom are among the companies that will be affected.

Analysts are predicting the New York Stock Exchange will fall by around 10% when it reopens this afternoon, but companies directly affected by last week's tragedy are likely to see much greater falls in the value of their shares.

Billions of dollars-worth of advertising revenue are expected to be lost as a result of last week's terrorist attacks in the US after broadcasters pulled all advertising from their schedules to provide uninterrupted rolling news.

Many advertisers, including virtually all of the world's major airlines, have stopped all marketing activity for the foreseeable future.

Others have adopted a low-key approach, wary of doing anything that might be considered tasteless at a time when the media is dominated by the tragedy.

The crisis has added to the woes of the advertising industry, which was already suffering from a global recession.

Advertisers were this week making a cautious return to the airwaves, but some sectors will take years to recover from the blow.

The crisis is also expected to hit US consumer confidence, which had remained high despite the economic slowdown. If that happens, the outlook for the advertising industry will become even bleaker.