Abdel-Rahman Saleh Abdel-Rahman al-Mutab, who was No. 4 on the list of the kingdom's 15 most-wanted suspects, was fatally shot north of Riyadh, the security official said, speaking on condition of anonymity because he was not authorized to speak to the media.
Police had been chasing al-Mutab since he escaped from the running gunbattle in which fellow militant Mohammed Abdel-Rahman Mohammed al-Suwailmi, No. 7 on the most-wanted list, killed five policemen before being fatally wounded Tuesday, officials said.
The deaths of the two militants brings to 10 the number of people on the most-wanted list who have been captured or killed. The list was issued in June.
The latest clash began Tuesday when al-Suwailmi shot and killed two policemen in a drive-by attack outside the city of Buraydah, northwest of Riyadh, the Interior Ministry said in a statement Wednesday.
He then sped 12 miles southwest and sprayed gunfire at a security checkpoint near the town of Al-Midhnab, killing three more officers, the agency said.
Police chased the car and fired at it. Al-Suwailmi was wounded, captured and died later of his wounds, the statement said.
The ministry said a second militant escaped by hijacking a woman's car at gunpoint, forcing her and her driver out. The security official identified the militant as al-Mutab, but he could not immediately give the circumstances in which al-Mutab was killed.
Police found several grenades and other weapons in the car after al-Suwailmi was captured, the ministry said.
Al-Suwailmi, 23, was involved in recruitment and propaganda for Islamic militant groups, the Saudi-owned Al-Arabiya satellite television reported. It was not immediately clear whether he was directly linked with any specific attacks.
Saudi officials reported in September that police killed al-Suwailmi along with four other militants in a gunbattle in the eastern city of Dammam. But al-Suwailmi soon afterward released an audiotape on the Internet saying he was still alive, and Saudi authorities backed off the claims.
The kingdom is waging a campaign against Islamic militants who have staged numerous terror attacks since May 2003, several of them targeting Westerners holding important positions in the oil industry in a bid to cripple the economy.
From an initial most-wanted list of 26 militants issued in December 2003, all but one have been killed or captured. Those on the newer list are mainly younger, middle-level militants.
King Abdullah, who ascended the throne in early August after the death of his half brother, Fahd, has vowed to push ahead with the crackdown.
Weeks after Abdullah's ascent to the throne, police carried out raids in Riyadh and the holy city of Mecca, killing six militants, including al Qaeda's leader in Saudi Arabia, Saleh Mohammed al-Aoofi, who was involved in the June 2004 kidnapping and beheading of the U.S. engineer Paul M. Johnson Jr.