The body of the man identified as Yosif Salih Fahd Ala'yeeri, one of 19 militants wanted for alleged ties to al Qaeda, was searched after he was shot dead following a police chase Saturday, al-Watan newspaper reported, quoting informed sources.
"The sources revealed that a folded handwritten letter, stained with blood, signed with the name bin Laden ... was found in the pocket of the killed," the paper reported.
It said the letter, dated in the Arabic calendar, was a season's greetings on the Muslim Eid al-Fitr feast, which was celebrated in December. It also gave a "blessing of the achievements of the groups associated with (bin Laden)," the sources told the newspaper.
The addressee could not be read because the letter was stained with Ala'yeeri's blood, Al-Watan said.
Ala'yeeri was among 19 al Qaeda operatives wanted by Saudi authorities following the discovery of a weapons cache in the capital on May 6. The government said at the time that the militants, 17 of whom were Saudis, were believed to take orders from al Qaeda leader bin Laden.
The group was also linked to the May 12 bombings at foreign housing compounds in Riyadh that killed 35 people, including nine attackers.
If the letter is confirmed as being from bin Laden, it not only would provide evidence the terrorist leader was alive late last year, but that there are ties between the Riyadh bombings and bin Laden's al Qaeda.
Saudi officials could not be reached for comment. There was no way to independently verify if the letter really came from bin Laden.
Four of the six identified Riyadh bombers were among the 19 wanted, according to Saudi authorities.
Thirteen of the group are still sought by the authorities, including an Iraqi with Kuwaiti and Canadian citizenship.
The newspaper said police worked for hours to detonate explosives Ala'yeeri had strapped to his body. He was also carrying four identification cards, a driver's license that does not belong to him, and a global positioning device, the paper said.
Saturday's car chase began at a checkpoint outside Turba, 124 miles north of the northern city of Hail.
The Interior Ministry official said that Ala'yeeri and his companion threw a hand grenade at the police during the chase, killing two officers and injuring two others.
Ala'yeeri's companion was identified as Abdullah bin Ibrahim bin Abdullah Alshabrami, who escaped but was later arrested north of Hail, the ministry said.
In an interview with the London-based Asharq al-Awsat newspaper, Ala'yeeri's father said he had not seen his son for years.
"He is dead now, in a way that we wouldn't have hoped to see any of our country's sons go," Saleh Ala'yeeri said from his home in Dammam, in the eastern part of the Kingdom.
Also, Saudi authorities in the southern province of Najran foiled "a large operation to sell (illegal) weapons" last Thursday, a statement by the ministry issued Monday said.
The authorities traced Saeed bin Faraj Al-Mihri, a Saudi national, as he was trying to sell a truck load of Kalashnikov rifles and ammunition in Najran, some 500 miles south of the capital, the statement said. Al-Mihri received 135,000 riyals ($36,000) for the 100 rifles and the ammunition. But he was encircled as he was working out the deal, and fired at the police, hitting one police vehicle. Al-Mihri was shot and died of his wounds in the hospital, the statement said.
Najran is on the border with Yemen, which is often cited by Saudi authorities as a source of smuggled weapons.