The $3.8billion Dakota Access pipeline began shipping oil for customers on Thursday, as Native American tribes that opposed the project vowed to continue fighting.

Dallas-based Energy Transfer Partners announced that the 1,200-mile line carrying North Dakota oil through South Dakota and Iowa to a distribution point in Illinois had begun commercial service.

The Dakota Access pipeline and the Energy Transfer Crude Oil Pipeline from Illinois to the Gulf Coast together make up the $4.8billion Bakken Pipeline system, which ETP said has commitments for about 520,000 barrels of oil daily.

'The pipeline will transport light, sweet crude oil from North Dakota to major refining markets in a more direct, cost-effective, safer and more environmentally responsible manner than other modes of transportation, including rail or truck,' the company said in a statement.

Dallas-based Energy Transfer Partners announced that the 1,200-mile line carrying North Dakota oil through South Dakota and Iowa to a distribution point in Illinois had begun commercial service. Pictured is the pipeline during construction in 2016

Grow America's Infrastructure Now, a coalition of businesses, trade associations, and labor groups that benefit from infrastructure development, issued a statement saying projects such as Dakota Access 'are key components to unlocking our nation's economic potential and creating jobs.'

Four Sioux tribes in the Dakotas are still fighting in federal court in Washington, D.C., hoping to persuade a judge to shut down the line.

Tribes and environmental groups fear it might pollute water sources.

More than half a year of protests in North Dakota resulted in 761 arrests before President Donald Trump's administration and the courts allowed the pipeline to be completed earlier this year.

But four Sioux tribes in the Dakotas are still fighting in federal court in Washington, D.C., hoping to persuade a judge to shut down the line. Pictured are protesters against the pipeline in November

'Now that the Dakota Access pipeline is fully operational, we find it more urgent than ever that the courts and administration address the risks posed to the drinking water of millions of American citizens,' Standing Rock Sioux Chairman Dave Archambault said in a statement.

'This pipeline became operational today, yet it has already leaked at least three times.'

The leaks came as the line was being prepared for service.

The Dakota Access pipeline and a feeder line leaked more than 100 gallons of oil in western North Dakota in separate incidents in March, and the Dakota Access line leaked 84 gallons of oil in northern South Dakota in April. No waterways were affected.