A suicide bomber blew himself up Thursday near a NATO convoy in southern Afghanistan, injuring five civilians including three children, police said.

The explosion occurred near a taxi stand west of Kandahar city, said provincial Police Chief Hesmatullah Alizai.

Alizai said the blast wounded five civilian bystanders, three of them children. NATO officials did not immediately have details of the attack, but Alizai said there were no NATO casualties.

Earlier in the day, another suicide bomber attacked a NATO convoy in Kandahar province's Zhari district but there were no alliance casualties, said Capt. Andre Salloum, a spokesman for NATO's International Security Assistance Force.

The attacks occurred as about 4,500 NATO and 1,000 Afghan troops launched the alliance's largest-ever offensive in Afghanistan on Tuesday in neighboring Helmand province.

The new mission aims to secure the lawless province, which is the world's biggest opium poppy-growing region.

"Since the operation started in Helmand, our enemies, the Taliban, are trying to disturb us inside Kandahar city," Alizai said.

NATO troops, aiming to put pressure on suspected Taliban in the north of Helmand, targeted militant strongholds and ammunition storage sites in Garmser district, the alliance said in a statement.

The troops clashed with suspected militants on Thursday but halted the confrontation after the militants moved into a civilian area, NATO said.

There were no reports of NATO or Afghan casualties during the clash.

Visit FOXNews.com's Afghanistan Center for complete coverage.