The leader of Afghanistan's interim government said Sunday that more suspects had been arrested in the killing of the country's aviation minister and vowed that the perpetrators would be dealt with "very, very sternly." 

"There will not be any lenient hand there. They will be given to justice — they have committed a murder," Hamid Karzai told reporters in the capital, Kabul. 

Abdul Rahman, the tourism and aviation minister, was killed Thursday under mysterious circumstances at the Kabul airport. Karzai has blamed the killing on a conspiracy involving members of his own government, and said it sprang from a personal vendetta. Official accounts and witnesses initially said Rahman was attacked by a mob angered by a lack of flights to Saudi Arabia for the annual hajj, or pilgrimage. 

Karzai also said he expected that three senior government officials wanted in connection with the minister's death would be returned to Afghanistan from Saudi Arabia, but did not specifically say whether they were yet in Saudi custody. He said he was meeting later Sunday with the Saudi ambassador to Pakistan to discuss the case. 

Asked about a series of violent incidents that have raised concerns about interim government's ability to keep order, Karzai suggested that if things do not get better, he might seek a tougher mandate for the peacekeeping force. 

"If the security environment of Afghanistan does not improve further, we will make sure that the international security forces will be asked, together with the Afghan forces, to take a stronger role," he said. 

But he added: "I said 'if' — we have not asked it." 

The international peacekeeping force said Sunday that an exchange of fire it reported a day earlier took place in the same area and at the same time that a group of civilians said they were shot at while trying to take a pregnant woman to the hospital. 

A 20-year-old man was found shot to death near the scene, the peacekeepers said. 

The peacekeepers insisted that the British paratroopers involved in the shooting were fired on first. Both parties — the civilians and the peacekeepers — said the shooting took place at about 1:20 a.m. Saturday, in a hillside slum facing an abandoned grain silo being used as an observation post by the peacekeepers. 

Capt. Graham Dunlop, a spokesman for the British-led force, said a six-man British patrol fired shots only after they themselves had been shot at. 

"The soldiers identified the firing point and they returned fire," he said. Dunlop said there was more than one gunshot, but did not know how many rounds the soldiers fired. 

Karzai, asked about the incident, said "the circumstances are not clear" but that there had been "some sort of incident of firing" in which one or two shots were fired at the peacekeepers' post. 

A short distance from the silo, a group of civilians said they had tried to take a 21-year-old woman named Faria to the hospital to give birth. 

In the group, they said, were the woman's husband, 25-year-old Mohammed Isaq; his 20-year-old brother Amaun, who was killed; the woman's mother-in-law and a neighbor who was driving the car. 

"They started shooting after the car engine started and the lights were turned on," said Mohammed Din, an uncle of the slain man, who was present when the shooting erupted. He said Amaun died instantly and the driver was wounded. 

Isaq, who showed a bandage where he had been wounded in the arm, said peacekeepers came to the house at about 3:30 a.m., but his brother was already dead and his wife had given birth to a boy. 

His wife showed what appeared to be superficial shrapnel wounds to her neck and knee. The baby boy appeared to be healthy, the family said. 

"We did not have any weapons of any kind," said Isaq. Family members did not say who they thought had fired on them. 

Dunlop said the incident was under investigation. 

In another development Sunday, U.S. jets bombed a former Al Qaeda training camp near the Pakistan border, residents of the area said by telephone. 

Four jets dropped a total of six bombs shortly before dawn in the Khugai area of Paktia province south of Kabul, according to one resident, Munir Hussein Tori. 

He said the camp was believed to be deserted and he did not know of any casualties. The area is about 9 miles from the village of Zawar, where U.S. Special Forces have been seeking Al Qaeda and Taliban renegades. 

The bombing would be the first since U.S. jets attacked an Al Qaeda camp in Zawar on Jan. 14. 

Meanwhile, Afghan tribesmen opened fire on the forces of a provincial governor trying to mediate a land dispute, killing two soldiers, an official said Sunday. 

The fighting erupted after some 200 soldiers loyal to the governor of Khost tried to mediate a dispute between the Gurbez tribe, which recognizes the central government, and the Kochi tribe, which does not. Governors are appointed by the central government. 

Kochi tribesmen refused to accept the mediation and opened fire on the soldiers, killing two and wounding one, said Amanullah Zadran, the minister for tribal affairs. He did not say when the fighting took place. 

In other developments: 

—Iran's Foreign Ministry denied a report by leading Iranian daily Hayat-e-Nou that Ayman al-Zawahri, Usama bin Laden's right-hand man, was arrested several days ago and is imprisoned in the capital of Tehran. The report did not cite named sources. 

—A visit to Germany by Karzai that was to start Sunday has been postponed, the German government said. The decision came after heavy snowfall forced German Foreign Minister Joschka Fischer to cancel a planned visit to Afghanistan. Fischer had been expected to bring Karzai back with him to Berlin on his plane. 

—In southern Afghanistan, an Australian soldier fighting with the U.S.-led coalition was killed in a land mine explosion on Saturday, the Australian government said. The soldier, who was not identified, was a member of the Special Air Service Regiment.