Updated

An Italian anarchist group claimed responsibility for a functional letter bomb sent to the CEO of Deutsche Bank and indicated there may be two more explosive packages still out there, police said Thursday.

Investigators said they found a hidden, rolled-up letter, written in Italian, in the envelope addressed to Deutsche Bank CEO Josef Ackermann from the FAI or Federazione Anarchia Informale (Informal Anarchist Federation).

The letter claimed responsibility for the planned attack on Ackermann and referred to "three explosions against banks, bankers, ticks and bloodsuckers," AFP reported.

"Based on that one must assume another two mail bombs may have been sent," police said.

The FAI has claimed responsibility for several attacks in recent years against European institutions, including a letter bomb sent to the European Central Bank in Frankfurt in 2003.

The Swiss-born Ackermann, 63, is a household name in Germany, according to the Financial Times, and is one of few German chief executives to regularly be accompanied by bodyguards.

He had been scheduled to step down next May. He has often been considered a divisive figure since he took the helm of the bank in 2002, according to AFP, and earned a $12.7 million salary.

The brown envelope that arrived Wednesday was addressed to Ackermann and drew the suspicions of staff at Deutsche Bank's mailroom, who X-rayed the letter and alerted police.

"Initial investigations show it was a functional letter bomb," police said.

The package was said to have contained explosives and shrapnel, FOX News Channel reported Wednesday. Sources said the construction of the device was not sophisticated.

While there was no apparent link to the US, the incident caused Deutsche Bank branches in New York to ramp up security measures.

Paul Browne, the NYPD's deputy commissioner of public information, told FOXNews.com that an increased number of police officers were deployed to Deutsche Bank locations in New York.

According to Bloomberg News, an executive of a large US bank said authorities had asked Wall Street firms to put their mailrooms on alert.

Wednesday's letter bomb was not the first time a Deutsche Bank chief was targeted by terrorists.

In November 1989, bank CEO Alfred Herrhausen was killed by the left-wing terrorist group Red Army Faction in a sophisticated roadside bombing.