American and Afghan forces seized 16.5 tons of drugs and killed 34 militants during a three-day operation against a key insurgent stronghold in southern Afghanistan, a U.S. military statement said Thursday.

The seizure was one of the biggest by foreign troops in Afghanistan since 2001 and an indication of a nexus between the insurgency and the drug trade that fuels it.

The narcotics were taken following an operation in the village of Marjah, a major drug-processing hub in Helmand province, which is the world's largest opium poppy producing region.

"They hit them where it hurts the most in a main command node and in the wallet," said Col. Greg Julian, the chief U.S. military spokesman.

During the operation, which started May 19, the troops also discovered 45 tons of ammonium nitrate, ammonium chloride and other material for homemade explosives, the statement said.

A statement said forces discovered black tar opium, processed heroin and morphine — all of which are derived from poppy plants.

They also discovered a "massive supply of heroin-refining products," the statement said.

For years, U.S. and other western officials have said the booming drug production in southern provinces, where insurgency is strongest and the government weakest, is funding the Taliban's war.

The United Nations has warned that the Taliban and drug lords have pocketed hundreds of millions of dollars from the trade, which also feeds corruption among government officials.

The massive drug production complicates efforts to effectively fight the Taliban, which have made a violent comeback in the last three years following their initial defeat in 2001.

Attempting to reverse these trends, President Barack Obama has ordered most of the new 21,000 U.S. troops to join the fight in the south.

During the operation in Marjah, the coalition troops killed 34 militants and seized weapons, communication equipment, Russian-made night vision goggles and U.S. military vehicle parts, the statement said.

In other violence, seven militants died Wednesday after a firefight and airstrikes in the central Ghazni province, another U.S. military statement said.

The joint force was after a Taliban subcommander involved in attacks in eastern Afghanistan. The wanted man, who was not identified, was detained.

Another two militants were killed and six others detained after a clash near Helmand's capital of Lashkar Gah on Thursday.