SANAA, Yemen, Dec. 15 (UPI) -- Saudi Arabia's intelligence service has established a station in Yemen's capital ostensibly to help coordinate a joint campaign against northern Shiite rebels along the kingdom's border.
But its main task is understood to be hunting down the Yemen-based operatives of a resurgent al-Qaida that threatens the Saudi monarchy, and eliminating them with extreme prejudice.
The Saudis, longtime adversaries of the republicans who triumphed over the royalists in Yemen's civil war of the 1960s, have long distrusted their southern neighbors -- and still do.
But such is the mortal danger the House of Saud sees in a resurgent al-Qaida in Yemen, ancestral homeland of Osama bin Laden, it has set aside old feuds to go after the jihadists.
The Saudi General Intelligence Presidency, the kingdom's principal intelligence agency, set up its Sanaa operation in June following talks between King Abdallah and Yemen's president, Ali Abdullah Saleh, who has been in power for 40 years.
The service has been headed since October 2005 by Prince Muqrin bin Abdulaziz, younger half-brother of King Abdallah.
The GIP was followed several weeks later by a unit from the General Security Services, which is attached to the Interior Ministry.
The GSS answers to Prince Mohammed Nayef bin Abdulaziz, the deputy minister who heads the kingdom's counter-terrorism apparatus.
The prince, responsible for crushing al-Qaida's campaign in Saudi Arabia in 2007, narrowly escaped assassination by a Yemeni member of al-Qaida on the Arabian peninsula in his palace in Jeddah Aug. 27.
Both these powerful Saudi agencies, pillars of the monarchy, have been working with the Yemeni military's special forces. These are commanded by the son of the Yemeni president, Col. Ahmed Abdullah Ali Saleh, who is expected to succeed him.
Yemen's intelligence apparatus is widely believed to have been heavily infiltrated by Muslim radicals who support al-Qaida. So the extent of the Saudis' cooperation with their Yemeni counterparts is not clear.
But the unprecedented Saudi intelligence presence in Yemen underlines the deep concern in Riyadh about the renewed al-Qaida threat and the extent to which Saleh's beleaguered government has been unable -- or unwilling -- to crush either al-Qaida's growing strength or the stubborn Shiite rebellion.
Still, knowledgeable intelligence sources say the Saudis succeeded in capturing one of the jihadists' leading financiers, a Saudi named Hassan Hussein bin Alwan, with the aid of Yemen's Political Security Organization.
Alwan operated for a long time in Pakistan's northwestern tribal belt of Waziristan along the border with Afghanistan. He arrived in Yemen via Oman in April 2009 fleeing from Pakistani forces sweeping into the jihadist stronghold.
Saudi intelligence, tipped off by Pakistan's Inter-Services Intelligence directorate, grabbed him three months later.
The PSO, Yemen's lead counter-terrorism agency, is headed by Ghaleb al-Qimch. Its upper echelon is composed entirely of former army officers and it answers directly to President Saleh.
U.S. officials say it has been seriously compromised by jihadist infiltration.
The Americans suspect that the spectacular escape of 23 high-value jihadist prisoners from a supposedly maximum security PSO prison in Sanaa on Feb. 3, 2006, through a 140-foot tunnel was aided by PSO officers.
The escapees included several senior al-Qaida operatives convicted of involvement in the seaborne suicide attack on the USS Cole in Aden harbor on Oct. 12, 2000, that killed 17 sailors.
Sometime during the summer, King Abdallah of Saudi Arabia handed over several hundred million dollars to Saleh to help finance his security services efforts to seal the border with Saudi Arabia, according to Intelligence Online, a French Web site that covers intelligence affairs.
As the northern rebellion grew, with Saleh's forces unable to decisively defeat the tribal fighters, Riyadh began providing military aid, including tanks repainted in Yemen military colors, according to Intelligence Online.
The Saudi military finally moved against the rebels on Nov. 4, after they allegedly crossed the border and killed a Saudi border guard officer. That offensive continues, with the rebels claiming large-scale Saudi airstrikes against them.
According to diplomatic sources, the Saudi intelligence input has allowed Yemen's special forces, led by the president's son, to make some headway. But the rebels continue to hold out.
Riyadh and Sanaa claim that's because the rebels are backed by Iran, which Tehran denies. Still, the fighting is increasingly seen as a proxy war between the two titans of the Gulf, Iran and Saudi Arabia.
This may be preoccupying Riyadh for the moment, but for them the more serious threat is still al-Qaida.