A civil engineer from Athens was swindled out of 500,000 euros after falling victim to an elaborate Spanish-based scam which promised him riches, Attica police said yesterday after arresting two suspects. On a trip to Madrid two months ago, the unnamed man befriended a 44-year-old American woman and a 34-year-old Nigerian, who claimed to be the nephew of a government minister who wanted to invest in Greek construction projects. The pair demanded cash advances from their victim to free up capital. He gave them 500,000 euros but was still being pestered for more. He got suspicious, then invited the couple to Athens for a meeting and tipped off police, who arrested them in a hotel on Tuesday. A Greek woman and three more Nigerians are being sought in connection with the alleged scam.