The green-and-white bus in the dusty Kabul courtyard is outwardly indistinguishable from thousands of others on the roads here. But Afghan security forces believe this vehicle is anything but ordinary. The bus, say Afghan police and intelligence officials, belongs to a senior Al Qaeda operative and close associate of Osama bin Laden who was planning a terrorist attack involving chemical weapons-possibly against Americans or multinational peacekeepers.

"We believe that there are chemical agents stored in the vehicle," says Gen. Aziz Urakhmon Mail, an official in the security service of Afghanistan's interim government. "We have not searched it yet. We are waiting for specialists to come and examine it."

The bus, seized by Kabul police last Thursday, may or may not turn out to be an unconventional weapon. But Afghan security forces say the incident was only one in a cluster of potential attacks foiled by them around Jan. 17-the day that U.S. Secretary of State Colin Powell was in Kabul on an official visit.

Sources have told NEWSWEEK that political opponents of the Hamid Karzai-led interim government were also planning other terrorist attacks the day of Powell's visit-including a remote-controlled barrage of rockets aimed at the presidential palace and other targets, as well as a bomb set to go off at the headquarters of Afghan state TV and radio. "According to our reports, they prepared this for Colin Powell's visit," says a senior Afghan intelligence official. "They wanted to make explosions everywhere in the city."

A spokesman for the U.S. Embassy in Kabul has declined to comment on the claims. But events in the capital on that day did reflect increased tensions among other foreign agencies. "We had a threat last Thursday concerning a supposed suicide operation, a car bomb," says Lt. Col. Thomas Loebbering, spokesman for the German peacekeeping forces in Kabul. The United Nations, too, went on security alert, shutting down its Kabul guesthouse "for security reasons." Other humanitarian aid organizations also tightened up their own security in response to what they described as credible terrorist threats. "[U.N. representatives] implied [the threat] was specifically targeted," says John Fairhurst of the British aid group Oxfam. "I'm sure we're all quite nervous about the situation."

On the face of it, an apparent ability to cope with last week's potential terrorist threat represents a triumph for the infant Karzai government. But the tale of a thwarted Black Thursday in Kabul is also one of bureaucratic confusion and a disturbing reluctance on the part of the Afghan security apparatus to share information with the United States and its allies. (One informed U.S. source in Kabul said American officials were unaware of the bus seizure and the claims that it contained chemical weapons.)

Afghan security officials say that they did inform the U.S. military and the British-led International Security Assistance Force (ISAF) about the planned bomb and rocket attacks the day before Powell's visit. But when asked whether U.S. forces would be asked to assist in the investigation of the suspicious bus, General Mail replied: "We captured [the bus] and we want to complete the investigation. This is an Afghan matter. The Afghans found it and the Afghans want to neutralize it."

Perhaps more importantly, the planned attacks underline just how unstable the security situation remains in post-Taliban Afghanistan. In spite of the widespread popular perception that the war is over, the burgeoning reports of threats against foreign targets in Kabul suggest the conflict cannot be considered over even within the capital itself.

Outside of it, meanwhile, there are increasing reports of a return to warlordism and the continued presence of armed Taliban and Al Qaeda forces. Aid workers around the country tell countless stories of hijacked food shipments and refugee camps terrorized by armed intruders. Noor Mohammed, a truck driver for a private company hired to move wheat for the World Food Programme, said army soldiers stopped his truck outside Kabul earlier this month and demanded money. He stepped out of the truck and stretched out his arms to signal that he didn't have any money for them. "Suddenly, one of the soldiers smashed the butt of his AK-47 into my hand," he says, holding up a hand wrapped in blood-stained white gauze. Another truck driver for the same company says: "The problem is getting worse with each day. There is no security."

Meanwhile, there have been reports of armed Taliban walking the streets in Kandahar-despite a disarmament campaign initiated there by the local governor. In Kabul, too, the Taliban is still an occasional presence: Iranian radio reported on Sunday that police had detained five Taliban fighters trying to enter the city. "In a way we're back to the warlord era," says Haneef Atmar of the International Rescue Committee. "The warlords, the commanders, try to divert food, to deny access, to abuse the basic rights of people."

Many of the reports of continued Al Qaeda and Taliban activity center on eastern Afghanistan, particularly the region of Khost, where the United States says it recently ceased a weeklong campaign of airstrikes against Al Qaeda targets. And the story of the mysterious bus is bound to refocus attention on Jalalabad, home to a big Al Qaeda training camp that has reportedly been linked with bin Laden-directed efforts to develop weapons of mass destruction. The bus was intercepted on the Jalalabad-Kabul highway and bears a Jalalabad license plate. Afghan intelligence sources say that its owner, an Al Qaeda operative known only by his nickname, "Naim," hails from Jalalabad. They say he has been in communication with senior Al Qaeda officers who have remained in the region following the U.S. airstrikes against the nearby Tora Bora cave complex. "We have seen a lot of documents in Al Qaeda safe houses in Jalalabad, which was the biggest Al Qaeda base," says a senior Afghan intelligence official. "We have seen documents about making explosives and adding poison gas to them. We have seen the laboratory and the chemicals."

However, Afghan officials attribute the planned rocket and bomb attack to a different instigator-the Hizb-i-Islami group of Gulbuddin Hekmatyar, a former mujahedin leader and radical Islamist now living in exile in Iran. Hekmatyar, who expressed support for the Taliban after the September 11 attacks, accuses the Afghan government of acting as a puppet for U.S. interests. Afghan intelligence officials claim they learned of the planned attacks from an informant in the Pakistani border town of Peshawar.

A member of the Afghan security service took NEWSWEEK reporters to a wrecked car in a vacant lot about 250 yards away from the Kabul presidential palace to show them where nine rockets had apparently been prepared for the attack. "They were going to come back and attach wires to a remote-controlled device," he says. So far, no arrests have been made in connection with the rocket attempt-another loose end in the mysterious Jan. 17 affair. Judging by the traditional murkiness of Afghan intrigues, it's unlikely to be the last.