At least eight people were injured Tuesday when Colombian police used tear gas against commuters gathered at a Bogota bus terminal to protest poor service.

Protests were staged at at least seven terminals of the Transmilenio system, but the most serious situation occurred at the Suba station, where riot police in armored vehicles fired tear gas and chaos ensued.

Eight people were injured at the Suba station, including a man who hit his head when he fell from a height of 3 meters (10 ft.).

The man was undergoing emergency surgery at a nearby hospital, municipal authorities said.

"I have been informed that there is a blockage and there is one person injured," said Bogota Mayor Gustavo Petro, who arrived at Suba to try and calm the situation.

Three other people injured at the Suba terminal were also hospitalized, while four were given first aid on the scene.

A pregnant woman who was in the Venecia station was taken to the Veraguas Clinic for treatment of effects resulting from gas inhalation.

The demonstrations began very early in the morning when hundreds of users blockaded stations in different parts of the city to protest travel delays.

On his visit to Suba, Petro listened to the demands made by commuters regarding what they called the "terrible service" provided by the Transmilenio system as well as the disproportionate reaction by the police.

Transmilenio - which began operating on Dec. 18, 2000, and uses articulated buses that move about the city on exclusive routes - was praised early on as a model for public transportation policy, but in recent years signs of collapse began to appear due to the rise in the number of commuters along with operational and infrastructure deficiencies.

Transmilenio serves an average of 1.9 million passengers per day, meeting 30 percent of the public transportation demand in Bogota, a city of more than 7 million. EFE