LASHKAR GAH Afghanistan (Reuters) - The Taliban executed five people in a busy opium market in Afghanistan's southern Helmand province and left their bodies hanging overnight after accusing them of kidnapping a businessman, officials told Reuters.

The militant group has stepped up its fight for control of the southern region since June, launching a string of attacks on government buildings, seizing territory and imposing its brand of Islamic justice.

Thursday's public hanging, in the largely Taliban-controlled Kajaki district, was the second group execution reported in Helmand since the offensive began.

"Five kidnappers ... were hanged to death by an order from the Islamic Emirate's prosecution authorities," a Taliban spokesman, Qari Yousuf Ahmadi, said in a text message.

"We hanged them in order to teach others a lesson."

Mass public executions, common when the Taliban ruled Afghanistan from 1996, ceased after the movement was ousted in the U.S.-led invasion in 2001.

But the Taliban's reach in strategic provinces like Helmand has grown since U.S. and allied troops stepped up the pace of their withdrawal, under plans to hand over security to Afghan forces by the end of 2014.

British troops closed their last outpost in Helmand in May.

Tribal elder Abdul Ahad Mahsomi told Reuters the five bodies were left hanging in the area's main opium market until Friday afternoon.

More than half of Afghanistan's opium is produced in Helmand and its main highway is an import route for drug smugglers. Around 90 percent of the world's heroin is produced in Afghanistan and last year's crop was the highest on record, according to the United Nations.

Helmand's police spokesman said he believed the hanged men were innocent and were executed to punish civilians for failing to support the Taliban against the government.

"As they (the Taliban) are defeated in the battlefield they want to take revenge on local people and create fear," said Shah Mohammad Ashna.

After months of intense fighting in Helmand's Sangin district, an Afghan special force commander said on Thursday he had started talks with Taliban to end the bloodshed.

Taliban fighters also abducted 13 people who had been working to clear mines in central Ghazni province and were traveling to the capital Kabul late on Friday, officials said.

"We have already spoken to elders in the area to use their influence and speak to the Taliban to release them," Shafiq Nang Safi a spokesman for provincial governor said.

The Taliban has targeted people clearing mines before, accusing them of working for the government.


(Writing by Mirwais Harooni; Editing by Jessica Donati and Andrew Heavens)