Two suspected suicide blasts have killed at least 24 people in the Afghan province of Kandahar, officials say.
Kandahar has been the scene of three 'suicide attacks' in two days
A suspected bomber drove his motorbike into a crowd, killing 20 and injuring another 20 in Spin Boldak, the governor of the southern province said.
An earlier attack killed an Afghan soldier and three civilians in the city of Kandahar, officials say.
The attacks fuel fears that those hostile to the US presence in the country are copying Iraq's insurgents.
A defence ministry spokesman told the BBC the blast was the "work of the enemies of Afghanistan" - a term used to describe hardline Taleban militants.
Kandahar governor Asadullah Khaled told the BBC that government soldiers were among the casualties but did not specify how many.
He also alleged that the bombers came from Pakistan, "where they lived and received training".
As well as the four dead, six Afghan soldiers and 10 civilians were injured in the first attack, which targeted an army convoy, reports say.
Witnesses at the scene of the first attack in the city of Kandahar reported seeing blood and body parts scattered over the area.
But accounts of what actually happened differed.
A senior army official in Kabul said the attacker detonated explosives placed in a vehicle next to an Afghan army convoy.
But the army commander in Kandahar city, where the attack occurred, told the Associated Press news agency the blast was caused by a roadside bomb.
15 January 2006: Canadian diplomat and 2 Afghan bystanders killed in Kandahar
5 January 2006: 10 killed in Tirin Kowt, Uruzgan
November 2005: 3 civilians killed in Kandahar
September 2005: 12 killed outside Afghan army base in Kabul
May 2005: 3 killed in Kabul internet cafe
June 2005: 20 killed in Kandahar mosque
Another security official in Kandahar, who did not want to be named, told the BBC that a man who had strapped explosives to himself jumped onto a military vehicle and blew himself up.
He said he went to the scene minutes after the blast and talked to eyewitnesses who had seen the bomber jumping on to the military car in Kandahar's district four.
According to the official, security forces opened fire, injuring several civilians.
A Canadian envoy to Afghanistan died in a bomb attack in Kandahar on Sunday.
Two civilians were also killed in Sunday's attack, which took place as Canada seeks to triple its contingent in Afghanistan as part of an expanded Nato force.
A man claiming to be a spokesman for the ousted Taleban regime said it was behind the bombing, and warned that more violence would follow.