MEXICO CITY (Reuters) -- Pressured by frustrated citizens, Mexico City
                  officials vowed to take a tough line on protests after a demonstration brought
                  traffic to a standstill and clashes shut a food market, newspapers said on
                  Sunday.

                  "The Ministry of Public Security announces that, while respecting freedom of
                  expression, we will not permit the closure and the deliberate boycott of any
                  street no matter how small it is," said Rosario Robles, minister for
                  government in Mexico City, Reforma newspaper reported on Sunday.

                  The stance was announced after some 9,000 angry teachers marched
                  through the streets on Friday to demand the release of five arrested
                  colleagues. The march brought traffic in this city of 18 million to a standstill
                  for hours on Friday.

                  That was followed in the early hours of Saturday by violent clashes between
                  police and protesters angry about entrance fees at the city's main wholesale
                  fruit and vegetable market. The action halted trade and blocked off the area
                  for hours.

                  Alejandro Gertz, the capital's minister for public security, said officials would
                  apply already existing laws with renewed vigor against anyone blocking
                  public roads to traffic.

                  Those laws entail five-year prison sentences and fines of between 500 and
                  5,000 pesos ($50 and $500) -- large sums in Mexico where the average
                  worker earns only about $9 per day.

                  Officials have been under increasing pressure from frustrated residents to
                  stop the city being held hostage to small groups of demonstrators.

                  Mexico City's inhabitants must cope with one of the most polluted
                  metropolises in the world and marches and protests that halt traffic almost on
                  a daily basis.

                  In Friday's demonstration by teachers, the city's major arteries were cut off
                  and thousands of people were late or could not reach appointments. One
                  taxi driver said a woman rushing to a hospital gave birth in the street.

                  The protest was over the arrest of five teachers in November after they
                  stormed the Senate building, breaking windows, fighting security guards and
                  holding lawmakers hostage for 10 hours to demand higher wages and more
                  independence from the government.

                  Gertz said officials would not tolerate groups putting the city's food supply at
                  risk as happened with Saturday's clashes at the fruit and vegetable market.

                  Thousands of buyers who had come to the market on Saturday were turned
                  away empty handed, while 1,000 police patrolled the streets for miles
                  around to prevent any further outbreaks of trouble.

                   Copyright 1999 Reuters.