* Photos appear to be claim of responsibility for attack
* Four Saudi security men killed by militants
DUBAI, July 7 (Reuters) - Photographs attributed to Al Qaeda in the Arabian Peninsula showed scenes they said were from an attack on a Yemeni-Saudi border post on Friday, apparently a claim of responsibility for an attack that killed four security men.
Friday's attack began when six militants arrived at the Wadia checkpoint in the Empty Quarter desert area, which links Yemen's Hadramout province with Saudi Arabia, Saudi Interior Ministry spokesman Mansour al-Turki had said on Saturday.
The militants shot and killed the commander of a Saudi border patrol and seized his car. They made their way inside Saudi territory towards al-Sharurah, Turki said.
Security forces engaged the militants in the second car, killing three and capturing the fourth. In total, four security men were killed in Friday's attack and on Saturday two militants blew themselves up after being trapped inside a government building in southern Saudi Arabia.
The nine pictures were posted on Twitter and jihadi forums. Superimposed on the pictures was the caption "Exclusive to Ansar al-Sharia News", the name for AQAP's local affiliate.
They showed fighters preparing to launch a Grad rocket, a Grad rocket being fired, a truck apparently laden with explosives parked at a border gate, and the apparent explosion of the truck.
A Yemeni official has said the attackers were al Qaeda militants. The authenticity of the pictures could not be immediately verified.
The Wadia crossing is in the southeastern Yemeni province of Hadramout, which stretches from the port of Mukalla in the south to the Saudi border through arid valleys and empty desert, the kind of landscape that al Qaeda militants use to their advantage across the Middle East.
AQAP has been waging a campaign of attacks on Yemeni government targets, raising fears the violence could spill across the border to Saudi Arabia.
Saudi Arabia has been building the security fence along its border with Yemen since 2003, though work has often been interrupted by protesting tribesmen who say it prevents them accessing pastures for their livestock.
The kingdom, a key regional ally of the United States, overcame its own al Qaeda insurgency almost a decade ago but has watched with alarm the recent military advances by radical Sunni Islamists in neighbouring Iraq. (Writing by Yara Bayoumy; Editing by Tom Heneghan)