A homicide bomber crossed the border from Pakistan into southern Afghanistan on Tuesday and blew himself up in a crowded pedestrian area, killing three civilians and wounding eight, police said.

The man was standing with luggage in a line of people waiting to be checked by border police when he detonated his bomb, in the town of Waish, about 500 yards inside Afghanistan's Kandahar province, said Gen. Abdul Raziq Khan, the border security police in charge.

Khan said there were no casualties among the police.

Meanwhile in two related attacks in Helmand province, troops shot a suicide bomber who tried to enter an Afghan army recruitment center, about 45 minutes after a roadside bomb went off near a NATO convoy, police said.

Troops standing guard opened fire on the bomber, who had explosives hidden beneath his clothes, after he tried to enter the recruitment center in the provincial capital Lashkar Gah and failed to heed their warnings to stop.

The bomber blew himself up too far away to harm anyone seriously, and only slightly wounded two soldiers, said Mohammad Eisah, the province's deputy police chief.

The roadside bomb went off earlier just after a convoy of NATO vehicles had passed in the town, wounding two Afghan civilians, Eisah said. The NATO vehicle was undamaged.

Eisah said police believed the attacks were linked.

NATO-led troops last week launched their largest offensive yet in the northern part of Helmand, a stronghold for Taliban insurgents who have stepped up attacks over the past year and are threatening a fresh offensive this spring.

Helmand is also the hub of Afghanistan's world-leading opium and heroin trade that is believed to help fund the Taliban but also profits Afghan officials. The government has stepped up its poppy eradication efforts this year — angering some farmers and others who profit from narcotics.

Despite its efforts to destroy poppies, Afghanistan could still be headed for another record-breaking opium crop this year, the U.N. says.

Tuesday's violence followed a roadside attack in Bakwa district of neighboring Farah province which killed nine policemen, including a local commander. The district briefly fell out of government control last month, but security forces have since moved back in.