Workers in the largest logistics center in Spain, owned by global e-commerce giant Amazon, are striking over wages and overtime benefits.

Around 150 workers gathered early Wednesday at the entrance of Amazon's warehouse in the outskirts of the Spanish capital, setting off fireworks and vowing to stop anything coming out.

Labor unions called the strike a success, and said that 98 percent of the workers have stopped working.

Amazon said in a statement that its wages are "competitive." The company says it employs 1,500 full-time and temporary workers in its San Fernando de Henares center.

The workers' unions say that Amazon is offering a new collective agreement that lowers pay levels for nearly one third of the plant's workforce and also reduces overtime benefits.