Over 10,000 packages of marijuana were seized and 11 people were arrested in the operation [Reuters]

Mexican security forces have seized 105 tonnes of US-bound marijuana in the border city of Tijuana with an estimated street value of about $340m. 

Soldiers and police grabbed Mexico's biggest-ever pot haul in pre-dawn raids on Monday in three neighbourhoods after police arrested 11 people following a shootout, army General Alfonso Duarte Mujica said at a news conference.

The marijuana was found wrapped in 10,000 packages in houses and a parked lorry, before it was displayed to journalists by soldiers in masks.

The contraband was painstakingly wrapped and labelled with signs and logos for a series of specific distributors in the United States, the army said.

Boost for Calderon

The bust is good news for President Felipe Calderon, who has staked his reputation on beating back powerful drug cartels in a military-led campaign he launched in December 2006.

Calderon is under pressure to show his drug war is working as the death toll over the past four years climbs to nearly 30,000 people, putting Washington and foreign investors on edge and provoking alarm among many Mexicans.

Mexican cartels have grown extremely powerful over the past decade, while violence sparked by cartel rivalries has spread beyond long-troubled cities such as Tijuana and Ciudad Juarez to formerly peaceful places, including the wealthy industrial city of Monterrey and the Caribbean resort of Cancun.

Mexico is one of the world's top marijuana producers, exporting about 7,000 tonnes of the drug a year.

Marijuana and home-grown heroin together generate more than $10bn in exports for the cartels every year, according to private estimates.