A protest movement demanding the removal of leftist Sandinista commanders from the military has spread as demonstrators seized public buildings in another town.

Members of President Violeta Chamorro's United National Opposition coalition seized the government telecommunications office and staged sit-ins Friday night at several police stations in La Concepcion, 20 miles southeast of Managua.La Concepcion became the 17th town to join the Civic Movement to Save Democracy, which has largely been confined to the eastern and southeastern parts of the country.

The demonstrators want Chamorro's conservative, U.S.-backed government to take control of the military away from the Sandinistas. Chamorro defeated former Sandinista President Daniel Ortega in February elections.

But Ortega's brother, Gen. Humberto Ortega, also a Sandinista, is still commander of the military and the demonstrators want him fired.

The takeover in La Concepcion was peaceful. Hours earlier, former Contra rebels attacked a police station with AK-47 assault rifles in Nueva Guinea, 190 miles southeast of Managua.

The firefight left three former reb-els dead and 35 people wounded, including nine policemen. Authorities said one of the wounded died Friday night, but the victim was not immediately identified.

Five of 21 people arrested in Nueva Guinea were held on weapons charges, while the rest were released for lack of evidence.

Interior Minister Carlos Hurtado said the shooting incident was not related to the Civic Movement to Save Democracy. But members of the group began acting 10 days ago to back demands by the former Contras for land and economic aid the Chamorro administration promised them when they demobilized earlier this year.