UN chief Ban Ki-moon Thursday urged Afghanistan to make fighting drug trafficking a priority as opium harvests soar in the world's top producer, and said the world must help in the effort.

"Above all, the Afghan government must prioritise the issue of narcotics," Ban said in his opening address in Vienna of a Paris Pact meeting to fight drug trafficking in Afghanistan.

"Law enforcement agencies must work harder on eradicating crops, eliminating laboratories, keeping precursors from entering the country, and inhibiting drug trafficking," he urged.

The head of the UN drugs and crime office (UNODC), Yury Fedotov, also urged Afghanistan "to make this a national priority and to develop shared responsibility across all branches of government."

Afghanistan grows about 90 percent of the world's opium and production of the drug soared last year by 61 percent, according to the UNODC. The drug trade now makes up about 15 percent of Afghanistan's gross domestic product.

Ban also warned that "reducing supply is only half the story. There can be no real success without reducing the demand."

"We must stand with Afghanistan in this fight," he added.

"Nothing would be worse than inaction," French Foreign Minister Alain Juppe, the co-chair of the event, also said.

"We need institutions that are efficient, transparent and democratic," he added.

In a joint Vienna Declaration to be adopted Thursday, the participating states vowed their commitment to help Afghanistan, citing a "common and shared responsibility" and a need for "a global response, including addressing the demand and supply sides."

The Paris Pact was set up in 2003 to coordinate efforts to fight opium and heroin trafficking from Afghanistan, with 56 states and a dozen international organisations signed up.

"Without serious measures to destroy drug crops as it has been made for example in Columbia, we are going to fight symptoms rather than the disease itself," Russian Foreign Minister Sergei Lavrov, also co-chair of the event, said Thursday.

He proposed setting up a fund "to be used for channelling confiscated proceeds from drug trafficking to UN programmes on combating organised crime, corruption and drugs in Afghanistan."

On the sidelines of the conference, Juppe and Lavrov also met to discuss a French proposal to set up aid corridors into Syria amid a bloody crackdown on anti-regime protesters but made no comments to the press afterwards.

Russia stands as one of Syrian President Bashar al-Assad's last major friends, vetoing with China this month a Security Council resolution condemning the regime for the violence, despite a barrage of criticism.