Dutch banks ING and ABN Amro are being urged to end their investment in a controversial oil pipeline project in the US.

The construction has prompted violent clashes between the army and the Standing Rock Sioux Tribe who say construction of the pipeline through northern Dakota could affect its drinking water supply and put communities ‘at risk of contamination by crude oil leaks and spills.’

They also say the pipeline will threaten the environment and destroy Native American burial sites, prayer sites and culturally significant artifacts, CNN reported.

According to fair banking campaign group Eerlijke Bankwijzer, ING has pumped the equivalent of €233m into the project in direct loans. ABN Amro has lent $45m to companies which are involved with the project.

ING said in a statement it is concerned about what is going on and is investigating further. However, withdrawing from the project is not an option legally, news agency ANP quotes the bank as saying.

ABN Amro points out it is not one of the 17 banks actively funding the pipeline and says it is in ‘continuous contact’ with the companies it has backed. This includes ‘explicitly’ ensuring that its concerns about the project are known, ANP said.