BOGOTA, Colombia - Hundreds of troops took control of Peru's second-largest city yesterday after the government imposed a state of emergency to end violent street protests against the sale of two state-owned electricity generating companies.

The protests, which began Friday and are the largest since President Alejandro Toledo took office 11 months ago, prompted the government to ban public protests Sunday and suspend constitutional guarantees for 30 days in the city, Arequipa, and the surrounding province.

The protesters, worried that the $167 million sale of the regional companies, Egasa and Egesur, to a Belgian company would mean higher utility prices and layoffs, spilled into the center of Arequipa, a city of 1 million people.

Police used tear gas over the weekend to disperse crowds; one canister fired by officers killed a 25-year-old university student.

On Sunday a military helicopter rescued 11 American Baptist missionaries who had become stranded at the airport, transporting them to a nearby military base.