A joint U.S.-Afghan military operation has begun in the troubled Helmand province against Taliban fighters who have vowed to disrupt the August 20 presidential election.  

U.S. Marines say a new operation has begun to thwart the insurgents in southern Afghanistan, who pose the most serious challenge to conducting this month's national election.

The Marine Expeditionary Brigade says 400 Marines and sailors and 100 Afghan soldiers have launched "Operation Eastern Resolve 2."

The poppy-rich Helmand region is a primary route for Taliban fighters coming from Pakistan to participate in the insurgency in Afghanistan.  The focus of the offensive is a southern valley, where the insurgents have been well-entrenched.  The troops hope to push the Taliban outside towns so civilians can go to the polls during the August 20 election.

In Kabul, Canadian Brigadier General Eric Tremblay of the NATO-led International Security Assistance Force says Afghan and foreign troops will be operating, across the country, to provide security for the first presidential election in five years.

"So our focus remains on preparing the way for the elections by confronting the insurgents, denying them the freedom to operate, isolating them from the population and degrading their capability," he said.

International organizations, including the United Nations, say Taliban violence and intimidation are disrupting election preparations and there is a fear they will prevent significant numbers of Afghans from voting.

President Hamid Karzai, running for re-election, has encouraged the public to not let such threats deter them from going to the polls.

The presidential palace confirms insurgents carried out a pre-dawn attack on a government compound in northern Kunduz province, where the Taliban have become increasingly active in recent months.  Mr. Karzai issued a statement praising the "patriotic sacrifice" of the police chief of the Archi district, who died repelling the attack.

Officials say the police chief managed to kill and wound some of the attackers. 

And in Paghman district of Kabul province, about 20 kilometers west of the capital, a remote-controlled bomb late Tuesday killed five policemen and wounded the district police chief and two other officers.

Meanwhile, two foreign journalists have been wounded near Kandahar.  The Associated Press crew was traveling with a U.S. military unit, when its vehicle was struck by a roadside bomb.  A Spanish photographer, based in Islamabad, lost a foot as a result of leg injuries.  His colleague, an Indonesian videographer, suffered leg and rib injuries.  

Six civilians, including women and children, were reported killed Tuesday in Kandahar when a mini-bus they were riding in was hit by a bomb.  The Taliban are also blamed for that attack.