German and U.S. officials have warned of the possibility of a terrorist attack, and security measures have been increased.
In July 2006 two gas bombs were placed on commuter trains but did not explode. Officials said that attack was motivated by anger over cartoons portraying the Prophet Muhammad in a Danish newspaper. Several suspects are on trial in Lebanon, and a Lebanese man has been charged in Germany.
Wolfgang Bosbach, a top legislator for Chancellor Angela Merkel's Christian Democrats, pointed out the anniversary of the Sept. 11 terror attacks next week, as well as deliberations by the German parliament in the next few weeks over whether to extend its troop mandates in Afghanistan.
"We are in a highly sensitive period," he said.
Chancellor Angela Merkel said in an interview released Wednesday that German troops would remain in Afghanistan for several more years, despite recent setbacks in the region. "To walk away would send the wrong signal," Merkel told N-24 television.
Robert Payne at Fraport AG, which operates Frankfurt International said that it was "business as usual" at the airport, but had no further comment about the arrests or any details about the alleged claims of the facility being a target.
Navy Capt. Jeff Gradeck, spokesman for the U.S. military's European Command in Stuttgart said German authorities had contacted them concerning the alleged plot, but had no further information.
"We extend our gratitude to Germany for their efforts in protecting us," Gradeck said.
Ramstein is one of the best-known U.S. Air Force bases worldwide because it serves as a major conduit for U.S. troops moving in and out of Europe, Asia and the Middle East. It is a key transit point for injured troops from Iraq and Afghanistan who are flown there to be taken to nearby Landstuhl.
On Tuesday, Denmark's intelligence service said it thwarted a bomb plot and arrested eight Islamic militants with alleged links to senior al-Qaida terrorists.
Ziercke said that although there were similarities to the group arrested in Denmark on Tuesday, no direct connection between the two had been established.
The Tuesday arrests in Denmark sent jitters through a country that was the focus of Muslim anger and deadly protests over the cartoons. Jakob Scharf, head of the PET intelligence service, said that the eight suspects arrested were "militant Islamists with connections to leading al-Qaida persons."
The European Union's top justice official said Wednesday that the threat of a terror attack remained high in the 27-nation bloc. EU Justice and Home Affairs Commissioner Franco Frattini said the EU executive would push ahead with plans to set up an EU-wide airline passenger data recording system despite privacy concerns.
"The threat of new terror attacks continues to be high," Frattini said, citing Spain, Italy, Belgium, Britain and Germany as countries where the risk has been the highest.