Two aid workers and a soldier have been killed by suspected Islamic militants in Afghanistan's unruly southern province of Kandahar, an official said.
Afghan troops have launched a massive manhunt for the attackers
The local men were gunned down at their office in Panjwai district, police chief General Salim Khan said.
The soldier died in a near-simultaneous attack on government buildings nearby.
Afghan authorities have blamed a recent rise in violence on Taleban fighters who have sworn revenge on US-led forces that ousted them from power in 2001.
Some 200 government troops have been mobilised to hunt down the assailants, Gen Khan said.
The murdered aid workers were employees of a Western-funded relief agency, the Coordination of Humanitarian Assistance (CHA), which operates in the fields of health and education.
Taleban rebels had earlier declared they would target foreign soldiers and civilians as well all Afghans who choose to work with them or with the administration of President Hamid Karzai.
The attack on Monday night is the second one targeting relief agencies in Panjwai.
The Taleban were blamed for an attack which damaged property belonging to the Central Asian Development Group last Friday.
There has been no confirmation from Taleban sympathisers or spokesmen that they were behind the latest violence.
Gen Khan said the attackers drove up in cars and sprayed their victims with fire from assault rifles.
"As a result of the attacks, two CHA employees were killed," he said, adding "one government soldier was killed and six others were wounded in the other attack".
Gen Khan said his men pursued the attackers as they fled southwards and killed two of them.
A US military spokesman said on Monday that attacks by suspected Taleban fighters had been increasing steadily.
More than 650 people have died since August - Afghanistan's bloodiest spell since the Taleban's ouster.
Guerrilla attacks on the US-led forces hunting al-Qaeda and Taleban remnants in the south and east of Afghanistan are relatively commonplace.
The more recent tactic of targeting of aid workers has led to a scaling down of reconstruction work.
The violence could dent enthusiasm for September's elections
The United Nations frequently assesses the risk its staff face in several parts of the southern and eastern Afghanistan, after a French UN refugee official was gunned down in the town of Gardez last year.
A roadside bomb in the city of Kandahar targeted - but missed - a passing convoy of UN electoral workers last week.
The violent upturn comes at a critical moment as President Karzai tries to prepare Afghanistan for national elections, due in September.
Observers say the difficult work of registering voters and persuading them to participate in the polls is routinely hampered by rising instability.