The niece of Paul M. Johnson Jr. (search), held hostage in Saudi Arabia by terrorists who claim they will kill him by Friday if their demands are not met, thanked the family's New Jersey community for their love and support at a vigil Thursday.

Angel Roork thanked a crowd of about 100 who attended a candlelight vigil for Johnson Thursday night, the crowd singing "Amazing Grace" and "God Bless America" as they prayed -- often holding candles and small flags. Roork said the community support has been helpful to the family as they await word on Johnson's fate.

Johnson's daughter, Tamara, also attended the vigil in a field in the West Creek section of Eagleswood (search), where he grew up.

"Your love, your prayers and your support are appreciated," Roork, of Little Egg Harbor Township, said during the 40-minute service, which was simulcast by a Christian radio station.

Both women were escorted to their car and drove away weeping, with Tamara Johnson (searchholding her hands to her face.

Johnson, 49, who has worked in Saudi Arabia for Lockheed Martin (searchfor more than a decade, was kidnapped Saturday by a group calling itself Al Qaeda in the Arabian Peninsula.

In a statement posted on the Internet on Tuesday, Johnson's captors threatened to kill him if Al Qaeda prisoners in Saudi Arabia were not freed within 72 hours. The 72 hours ends sometime Friday; the kidnappers did not specify what time the countdown began or when it ends.

Earlier Thursday, Johnson's son Paul Johnson III pleaded for his release.

"I just want to ask the president of the United States and the Saudi officials to please make this happen," the son said in an interview on NBC's "Today" show. "Father's Day is right here. Bring my father home for Father's Day."

Before the vigil, tears streamed down the face of Sam Sprague, 48, as he talked about his childhood friend.

"Do whatever you gotta do, buddy, to get out of there. Dig till you ain't got no fingernails left," Sprague said.

Sprague, who now lives in Stafford Township, said he and Johnson grew up hunting, racing bikes and model cars, and picking blueberries and holly to make money.

Johnson, who works on targeting and night vision systems for Apache helicopters, is a longtime Saudi Arabia resident who respects the country's culture and traditions, his family said.

"He loves the country and the Saudis owe it to my father -- he's been there 12 years -- to bring my father home alive," his son said.

'Believer' Asks for Mercy

A letter signed "The Believer" urges the militants to spare Johnson, saying killing him would violate Islamic law. "I will curse you in all my prayers" if he is harmed, it warned.

The letter was posted late Wednesday on Web sites where Al Qaeda supporters and other militants leave messages, and aired on a Saudi-owned television network, al-Arabiya.

Meanwhile, a senior Saudi official in the United States directly familiar with the investigation said Thursday night that U.S. and Saudi officials have had few promising leads in their search for Johnson. The group Al Qaeda in the Arabian Peninsula (search) is believed to be headed by Abdulaziz Issa Abdul-Mohsin al-Moqrin, the top Al Qaeda figure in Saudi Arabia.

The Saudi official said there had been no communications from the kidnappers except for the video and written statement they posted Tuesday on a Web site.

Saudi newspapers on Thursday quoted unidentified government officials as saying the kingdom would not give in to the demands of terrorists.

The letter Wednesday, signed by Saad al-Mu'men -- a pseudonym meaning "Saad The Believer," -- identified the writer as a Saudi friend of Johnson's and said he had bestowed his protection as a Muslim on the American hostage.

If Johnson is harmed, it read, "I will never forgive you. I will curse you in all my prayers." It pointed to a saying by Islam's Prophet Muhammad: "If they were granted [Muslim] protection, then killing or taking their money or harming them is forbidden."

The Saudi official in the United States, who spoke to The Associated Press only on condition of anonymity because of the sensitive nature of the probe, said the FBI had sent a team of about 20 specialists in hostage rescue, hostage negotiations, profiling and other specialties who were working directly with Saudi officials.

More than 15,000 Saudi officers have been conducting a citywide search of Riyadh, going door-to-door in some neighborhoods considered hotbeds for terrorist sympathies and conducting surveillance in other parts of the city.

"We are even using the fire department, for instance, because they have knowledge of their neighborhoods, and districts," the official said. More than 1,200 Saudi homes had been searched as of Thursday night, the official said.

The Saudi official also said the chief suspect in Johnson's kidnapping, al-Moqrin, is also the main suspect in the shootings of a German citizen and an American in the kingdom recently.

The official said the Saudi government has directly communicated with Johnson's son in New Jersey to apprise him of the full extent of the search.

Security has been increased in and around Riyadh as the hunt for Johnson continues.

In the letter, al-Mu'men said Johnson had expressed opposition to U.S. foreign policy and an interest in converting to Islam.

"He was interested in reading Quran translations ... I swear to God that once he said to me in public -- in a popular restaurant in Riyadh: 'I hate my country's politics. I am interested in Islam. If I convert, I will go and live with my wife in East Asia," al-Mu'men wrote. Johnson's wife is Thai.

Al-Mu'men said he was a colleague of Johnson but did not give any details about his job. He said he often invited Johnson for dinner and gave the American books on Islam as presents.

The letter was posted on Web sites know for Islamic extremist writings and was subsequently posted on the Web site of the Saudi-owned satellite television channel Al-Arabiya, http://www.alarabiya.net.

Al-Arabiya said that al-Mu'men said in an interview that he chose Islamic Web sites known for airing radical views because he was sure the kidnappers would monitor them.

Other contributors to the sites where the letter was posted ridiculed the message and called for Johnson's death.

Al-Arabiya told the AP that al-Mu'men had contacted the station but agreed to be identified only by the pseudonym. The station said it had confirmed the man it interviewed was the author of the letter, but it did not say how.

Al-Mu'men refused an interview with the AP in a message relayed through the station.

Amid concern over Johnson's fate, the U.S. State Department updated a 2-month-old travel warning for Saudi Arabia, pointing out that attacks on Americans there have resulted in deaths and injuries and, in a reference to Johnson, a kidnapping.

A department statement reminded American citizens of "the continuing serious threat to their safety while in Saudi Arabia." It noted that private American citizens are being strongly urged to depart the country.

The Associated Press contributed to this report.