Bangladesh (Reuters) - Nearly a thousand large turtles have washed up dead on Bangladeshi and Indian beaches in the Bay of Bengal in recent weeks, officials and activists said on Monday, blaming the deaths on fishing nets. About 200 turtles, some weighing 20 kg (44 pounds or more), have been found along the Bangladesh coast in the past week. Around 140 turtles were found dead along a 4-km (2.5 mile) stretch of beach near the southern tourist town of Cox's Bazar, said Mohammad Aminul Islam, deputy commissioner of Cox's Bazar district.More turtles were dying on the shores of St. Martin island, 35 km off the country's southeastern tip, Teknaf. Islam said he believed the turtles died after being caught in fishing nets.In eastern India, wildlife activists said dead turtles were also dotting beaches there in large numbers. "We counted 763 of them in the last two months, all dead after getting caught in fishing nets," Biswajit Mohanty, wildlife activist and coordinator of Operation Kachchappa (turtles), an Orissa-based group, told Reuters."They had bulging eyes and necks, which indicate they died due to a lack of oxygen after getting dragged underwater in fishing nets for hours," Mohanty said.The group surveyed a 200 km (124 miles) stretch of coastline in Orissa, near Paradip, a major Indian port. Bangladeshi fishermen, who have also reported that some dolphins have die, deny they are to blame, saying they don't catch many turtles, but when they do they are returned alive to the water.Marine officials said the deaths could be due to increased pollution or unknown natural causes. Bangladesh has a 90-km natural beach from Cox's Bazar to Teknaf, said to be the longest in the world, that is poorly maintained and monitored.