Taliban insurgents entered Naway-i-Barakzayi, a Helmand town north of Garmser, and clashed briefly with police before the security officials fled, an Afghan police official said.
The official said Taliban forces were now moving freely around the town and district.
In the Helmand town of Garmser, close to the Pakistan border, scores of Taliban insurgents overran Afghan policemen holed up in a compound on Sunday, driving the security forces and a handful of government officials to flee, another Afghan official said.
Major Scott Lundy, a spokesman for the US-led coalition in Afghanistan, said: "We are in contact with lots of people to build an accurate picture of the two districts in southern Helmand which are under control of the Taliban."
On Monday, a bomber killed three justice ministry employees after blowing himself up inside their offices in Helmand.
Three Afghan soldiers also died in a roadside bombing in the province.
In eastern Afghanistan, US-led troops killed four Arab and Chechen fighters, after raiding their hideout.
Taliban forces killed a coalition soldier and wounded 11 others in a battle on Monday in Tirin Kot, capital of Helmand's neighbouring Uruzgan province, a US statement said.
And hundreds of Canadian and Afghan soldiers raided Taliban strongholds in orchards in southern Afghanistan, causing fighting that killed at least 15 insurgents and one Canadian soldier.
A coalition air raid killed another 10 insurgents in the neighbouring Panjwayi district.
In recent months, Afghanistan has been gripped by the worst violence since the US-led invasion toppled the Taliban government in late 2001.
About 10,000 US, Canadian, British and Afghan forces have been deployed across southern Afghanistan as part of Operation Mountain Thrust to loosen the Taliban's hold on the region.
More than 800 people, mostly insurgents, have been killed since May, according to an Associated Press tally of coalition and Afghan figures.