Container handling at Colombia's main Pacific port, Buenaventura, has been paralyzed by a dockworkers' strike, union officials in this capital said Thursday.

Some 500 workers are taking part in the job action, which began Wednesday, the CUT labor federation said.

CUT officer Fabio Arias told Efe by phone that workers with the containers-handling firm Terminal Especializado de Contenedores de Buenaventura, or Tecsa, declared the strike.

Tecsa's contract workers also joined in the stoppage, according to Arias, who said these workers are demanding higher salaries, direct work contracts and an end to labor intermediation (abusive sub-contracting practices).

"The port is more than 70 percent paralyzed," the union leader said, adding that striking workers have stationed themselves at the entrance to the wharf.

Arias said security forces tried to dislodge the strikers from their position on Wednesday in an operation that left four workers injured and three arrested, although all have since been released.

Tecsa, whose majority shareholder is Sociedad Portuaria Regional de Buenaventura, is responsible for 85 percent of container traffic at the port.

An SPRB spokesman told Efe by telephone that the strike's impact on the terminal's operations has been "minimal."

This Pacific port handles nearly 60 percent of Colombia's foreign trade, which amounted to more than 10.11 million metric tons of import and export cargo in 2011 and roughly 5.81 million metric tons thus far in 2012.

Some 520,000 containers were moved through Buenaventura last year. EFE