Hundreds of foreign tourists are stranded at the Bulgarian Black Sea airport of Burgas after their charter flights were cancelled over a payment row between their tour operator and the flight carrier, officials said on Saturday, according to Reuters. Over 800 Russian and Finnish tourists could not return home after privately owned Bulgaria Air cancelled four charter flights to Moscow, St. Petersburg and Helsinki citing unpaid bills from Bulgarian tour operator Alma Tours. Alma Tours did not respond to phone calls on Saturday but in a statement to Focus News, it expressed \"deepest regrets that a trade dispute caused inconvenience and distress for the tourists and guests of Bulgaria\" and hope that a compromise could be reached to get the tourists home. Bulgaria has been struggling to lure back holiday makers to its coastal hotels and resorts since the global credit boom went bust in 2007. \"We will do all that we can to help the tourists,\" deputy Economy Minister Ivo Marinov said. \"This is very unfortunate as we have put in a lot of effort and have seen a 40 percent rise in Russian tourist visits this summer. But such a trade row hits the image of Bulgarian tourism,\" he said. A Bulgaria Air plane carrying 186 Russian tourists took off late on Saturday to Moscow after a Russian tour operator paid for the flight, Bulgarian news agency Focus reported, but a charter flight to Helsinki for Saturday and another scheduled for Sunday morning to Riga had been cancelled. Prime Minister Boiko Borisov has made available the government\'s own plane with 96 seats on board to transport some of the stranded Russian tourists to Moscow later on Saturday, the head of the plane\'s crew said.