Amsterdam/Washington, Aug 31 (DPA) Dutch police were Tuesday questioning two Arabs detained at Amsterdam's airport following a terrorist warning by the US Home Security Department.

Dutch TV network NOS reported the circumstances of the arrests were still unclear, but officials were investigating whether the men - presumed to be Yemeni nationals - may have been checking out the flights for possible terrorists attacks.

The men had arrived at Amsterdam's Schiphol international airport on a flight from Chicago Monday night. The Dutch public prosecutor confirmed the men, identified as Ahmed Mohamed Nasser al-Soofi and Hezem al-Murisi, were arrested "at the request of American authorities".

According to US media reports, the men had been carrying fake bombs in their checked baggage on previous domestic flights in the US. The ABC network quoted a senior US law enforcement official as saying: "This was almost certainly a dry run, a test."

Al-Soofi, resident in Detroit, Michigan, had attracted attention when he tried to embark on a flight from Birmingham Airport in the US state of Alabama to Chicago because he had been wearing voluminous clothes despite high temperatures.

Officials found $7,000 in cash, several mobile phones and watches taped together, as well as a carpet cutter and three other large knives in his luggage. The man had ultimately been allowed to continue his trip as no explosives were found in his baggage.

On landing in Chicago, al-Soofi had checked in his baggage for a flight via Washington to Dubai and Yemen. Instead of embarking on this flight, however, he had taken a plane to Amsterdam together with al-Murisi. The unaccompanied luggage had been taken off the other plane by officials.