Mazin Aman Allah, Aljazeera's correspondent in Kabul, reported that unidentified fighters attacked two vehicles carrying medical workers on Wednesday about 35km away from Kandahar.
Attackers opened fire on their vehicle as they drove through the desert after treating refugees in a nearby camp.
Two of the five dead were doctors. Three other medical workers in the vehicle were wounded, said doctor Abdul Qadir, director of UN and US-sponsored Afghan Help Development Services, a local aid group that employed the medical workers.
Casualties were transferred to Kandahar hospital.
Also on Wednesday, governor Jan Mohammed Khan said suspected Taliban fighters had been killed on Monday by US warplanes that bombed their hideout in Uruzgan province.
US military spokeswoman Sergeant Marina Evans confirmed the attack and said "several of the enemy had been killed".
International peacekeepers and
aid workers are often targeted
The governor added that six policemen were killed by suspected Taliban who ambushed their convoy in the same area on Tuesday.
One officer was still missing after the attack and feared dead.
Reinforcements had been rushed to the area "to hunt down
the Taliban", Khan added.
In other news, Aljazeera's correspondent reported four rockets being fired early on Wednesday morning in Kabul, a few hours before the arrival of the US secretary of state.
Terror of drugs
President Hamid Karzai, in a press conference with Rice, said there was "cooperation between the drug trade and
Afghanistan produces an estimated 87% of the world's supply of opium and heroin.
Rice (L) pledged that US troops
would stay for as long as needed
"We will have terrorism attacking [us] ... for quite some time," Karzai warned. He went on to say that fighting drugs was essential. "If we fail, we will fail as a state eventually and we will fall back in the hands of terrorism."
Rice said the 21,000-strong US-led coalition was doing its best to quash the insurgency.
"We are doing everything we can to defeat the terrorists. We cannot simply defend ourselves, we have to be on the offensive," she said.
Rice added that US forces would remain "for as long as they are needed in whatever numbers they are needed to make certain that they defeat the terrorists and Afghanistan becomes a place of stability and progress".
In the early Wednesday Kabul incident, at least four rockets exploded in the Afghan capital, one outside the Canadian ambassador's residence and another at the government's intelligence department.
The explosion outside the residence of the Canadian ambassador wounded a guard, who was rushed to hospital in serious condition, police at the scene said.
Nato peacekeepers surround the
Canadian envoy's residence
The second rocket landed inside an intelligence department office not far from the residence, police said, adding that no one was wounded in that attack but that it had caused some damage.
The Canadian ambassador's residence is tucked away behind a heavily fortified street of the diplomatic enclave, about 1km from the presidential palace, the US embassy and the headquarters for the Nato-led peacekeeping mission.
Two other rockets hit the outskirts of the city.
It was not immediately clear who fired the rockets, but a policeman guarding the site of the attack outside the residence blamed Taliban fighters.