LAGOS , Nigeria ( CNN ) -- Royal Dutch Shell said Tuesday that it may not be able to meet its oil supply obligations in Nigeria after an attack on its major pipeline . Heavily armed Nigerian rebels pose a constant threat to oil pipelines in the country . The Movement for the Emancipation of the Niger Delta ( MEND ) , a rebel group , said `` detonation engineers backed by heavily armed fighters '' sabotaged two of Shell 's pipelines early Monday . After a helicopter flyover of the area , Shell confirmed that parts of its large Nembe Creek `` trunk line '' were damaged , company spokeswoman Caroline Wittgen said . The company shut down some production `` to limit the amount of crude that will spill into the environment , '' she said . Hours later , it declared `` force majeure , '' a legal term meaning it could not meet its supply obligations in the region because of the attack . `` [ Shell ] is working hard to repair the line and restore production , '' Wittgen said . Nigeria is the fourth-largest supplier of oil to the United States , and attacks by rebels have helped fuel the year-long spike in crude oil prices . It 's one of many factors pushing up the price of gas in the U.S. , where one in every 10 barrels of oil comes from Nigeria . MEND -- the largest rebel group -- has targeted foreign oil companies since 2006 . It has bombed pipelines and kidnapped hundreds of foreign oil workers , typically releasing them unharmed , sometimes after receiving a ransom payment . MEND hopes to secure a greater share of oil wealth for people in the delta , where more than 70 percent of the population lives on less than a dollar a day . Its attacks on oil facilities have taken a toll . `` Anytime a pipeline is affected , anytime any production gets shut down , you see oil prices jump up one or two dollars a barrel just because there is no slack in the system , '' said Jim LeCamp , a senior vice president with RBC Wealth Management , which manages assets for wealthy clients worldwide . Exxon and Shell are two of several companies that have been extracting 2 million barrels of oil a day in Nigeria . Recent rebel attacks on oil pipelines in the Niger Delta have cut overall production by roughly 10 percent -- meaning 200,000 fewer barrels of oil on some days . That decrease in production comes at a time of increased demand from oil-hungry regions such as China , Russia and Latin America . `` Anytime there 's a disruption there , it really affects the system , '' LeCamp said in a recent interview with CNN .
Shell says it may not be able to meet supply contracts after Nigerian attack . Two of Shell 's oil pipelines sabotaged by rebel groups on Monday . Score: 6