Afghan authorities have arrested a judge for allegedly harboring the organizers of two bombings last year that killed about 12 people, including four Americans, and believe the ringleaders took their orders from an Iraqi member of Al Qaeda (search), a senior official said Saturday.

The purported link to Usama bin Laden's (search) terror network follows warnings from the U.S. military that foreign militants — mostly believed to have found refuge in neighboring Pakistan — were still operating in Afghanistan, three years after the start of America's War on Terror.

Gen. Abdul Fatah, a senior Afghan prosecutor, said a preliminary court judge called Naqibullah was detained about two weeks ago after two men accused of organizing an Aug. 29 car-bombing against U.S. security contractor Dyncorp (search) told investigators they stayed at his house in Kabul.

"He is accused of two things. First, he let the terrorists stay in his house. Second, he was aware of their activities but didn't inform anyone," Fatah told The Associated Press.

Naqibullah, who like many Afghans goes by one name, was the head of a preliminary court in the Panjshir Valley, north of Kabul, Fatah said.

U.S. military officials had no comment Saturday on the judge's arrest. But Maj. Gen. Eric Olson said in September that Al Qaeda-linked militants may have carried out the car-bombing.

Three Americans were among about 10 people killed in the attack on the office of Dyncorp, which provides bodyguards for President Hamid Karzai (search) and trains Afghan police.

Two months later, a suicide attacker laden with hand grenades blew himself up on a shopping street in the capital near a group of Icelandic peacekeepers, injuring three soldiers and killing an American woman and an Afghan girl.

Intelligence officials have identified the alleged ringleader of both attacks as a Tajik national called Mohammed Haidar and said he confessed. Fatah said an accomplice, Abdul Ahad, was arrested with Haidar. Ahad and Naqibullah are from the same district of Afghanistan's Kapisa province, he said.

The organizers, as well as a suicide bomber identified as a Kashmiri named Akbar, "stayed in his (Naqibullah's) house all the time, from the beginning to the end of their mission," Fatah said.

Afghan intelligence officials also said Haidar organized the attacks on the instructions of a suspected Al Qaeda member named Attaullah, who was based in Peshawar, in neighboring Pakistan.

Fatah said Attaullah was an Iraqi national.

"First, they brought another guy, also a foreigner, but in the end he didn't want to do it. So they took him back to Peshawar and brought Akbar," Fatah said in a telephone interview. "All three received their orders from Attaullah. He is an Iraqi who is outside the country. Without any doubt he is a member of Al Qaeda."

Pakistani intelligence officials in Peshawar, however, said they had no suspect with that name on their wanted list.

Fatah said the men would be tried once security forces complete their efforts to arrest further suspects. Several of Haidar's sons were suspected of aiding the bombers, but they remain at large, he said.

American military officials insist the re-emergence of the Afghan government and stepped-up counterinsurgency operations have put rebels on the retreat here, but they caution that Al Qaeda cells still could be operating in Afghan cities.

The U.S. military has said American and Afghan forces killed nine people and detained at least 18 others in a monthlong sweep against Al Qaeda suspects near the Pakistani border late last year.