The Washington National Guard has criticised two servicewomen for being photographed in military uniform while breast-feeding their babies.

The photos were posted on the Facebook website by a support group at Fairchild Air Force Base called Mom2Mom.

The group's co-founder, Trysta Chavez, said the photos were meant to promote World Breast-Feeding Week in August.

Military officials said it was a breach of the rules to use the uniform to promote non-military causes.

National Guard spokesman Captain Keith Kosik told the BBC that there was no regulation against breast-feeding in uniform.

But he said the National Guard took issue with the uniform being used "by an outside entity for a cause", regardless of whether it was a positive one.

Capt Kosik said the women were unlikely to face disciplinary action.

The Mom2Mom group, founded by Ms Chavez and Crystal Scott, posted a message on their Facebook page defending their actions, and insisting that they supported the military "110%".

"The military photographs were never meant to exploit, promote or to use the uniform to help our group," the message said.

"These were for our local community to raise awareness for World Breast-Feeding Week in August. Our mission is to help raise awareness, educate and support breast-feeding mothers."

The photos, taken by another military spouse at Fairchild, quickly went viral after being posted online.

"It's sad that this is such an issue," Ms Chavez said. "It's a taboo really."