Yemen's Houthi rebels on Wednesday claimed to have seized more than 20 positions inside Saudi Arabia, with rebel officials promising to release video footage of the daring attack later this week.

Houthi spokesman Yahya Sarei told the rebel-run SABA news agency that fighters crossed over the border to seize Saudi military positions in the kingdom's southwestern Najran province. 

Houthi forces carried out a "surprise attack carried out along three separate axes" over a 72-hour period, Sarei said, claiming that 200 Saudi troops were killed in the offensives and that military equipment were seized by the rebels.

"We have extensive video footage of the operation which will be broadcast later," Sarei said, according to Al Jazeera.

There has been no independent verification of the claims.

Saudi Arabia's Crown Prince Mohammed bin Salman - viewed as an architect of the Saudi-led coalition intervention in Yemen - visited troops on the border earlier this week.

Yemen has been in a state of war since Houthi rebels captured the capital, Sanaa, in 2014, forcing the government south.

The war intensified following the intervention of the Saudi-led coalition in March 2015, with at least 13,000 people killed and Yemen suffering one of the worst humanitarian crises in the world.

Much of the fighting has been focused on the key port of Hodeidah, with a Saudi-UAE led offensive on the city held back by the Houthis, while fighting has taken place in southern Yemen.