Syrian refugees stranded along the Jordanian border have said that clean water is getting scarce in their desert tent camp after the area was sealed by Jordan in response to a deadly cross-border attack.

Mobile phone footage taken in the Ruqban camp showed refugees chanting, "We want water." Three Ruqban residents said by phone that people have begun drinking polluted water.

Some 64,000 Syrians live in two encampments along the border, awaiting admission to Jordan. Many have been in the camps for months and depend on daily deliveries of food and water by international aid agencies based in Jordan.

Jordan declared the area a "closed military zone" after a car bomb attack launched from the Ruqban area killed six Jordanian troops and wounded 14 at dawn on Tuesday. There has been no claim of responsibility, but Jordan says it has evidence that militants, including Islamic State fighters, are present in the camps.

King Abdullah II warned after the attack that Jordan will "respond with an iron fist" to anyone harming its borders or security.

Jordan-based international aid officials confirmed Wednesday that the border area was sealed and that they couldn't send aid there. However, they gave conflicting accounts of whether any water had been delivered to the camps since the attack. The officials spoke on condition of anonymity because they were not authorized to brief reporters.

Jordanian government spokesman Mohammed Momani could not be reached for comment.

The UN refugee agency said it is working with other aid groups and Jordanian authorities to get water delivered. Agency spokesman Andreas Needham in Geneva said such deliveries are a priority, but would not elaborate.

The London-based rights group Amnesty International said that a total border closure and denial of humanitarian aid "would inevitably lead to extreme hardship among those unable to find refuge and put their lives at risk".

The group said Jordan has a right to protect civilians from armed attacks, but that its security measures "must not violate its international legal obligations to provide protection and assistance to refugees who are desperately fleeing the very same type of violence".

Ahmad al-Masalmeh, a Syrian opposition activist based in the southern border province of Deraa, said that innocent people have started "paying the price of the explosion".