A mine buried along the track went off as the train was at Navaladi in the the coastal district of Batticaloa, a military official in the area said by telephone.
"The engine and another compartment derailed after the explosion," the official said.
Sri Lanka's tsunami-ravaged eastern coast has been hit by months of fighting following the launch of a major government effort to oust Tamil Tiger rebels from the area and confine them to the north of the island.
furosemide
The latest attack also came as residents in Batticaloa, 300 kilometres (187 miles) east of here, prepared for the funerals of two ethnic Tamil Red Cross workers who were abducted and murdered last week.
premarin
The funerals are scheduled for Thursday, to coincide with a scheduled visit to the region by Japan's special peace envoy to Sri Lanka, Yasushi Akashi. The Japanese envoy arrived in Colombo Tuesday on a four-day visit aimed at reviving the island's tattered peace process.