The Nicaraguan army mobilized troops in the northern part of the country to track down a group of about 300 former Contras who attacked an army construction brigade, officials said Saturday.

"The army has mobilized troops of Region V . . . to pursue a group of armed ex-Contras who attacked soldiers working on highway construction," a military spokesman said.The army's press office said 300 former Contras attacked an army brigade Thursday morning in San Jose de Bocay, about 150 mile north of Managua, in Jinotega province. No casualties were reported.

"It seemed they (the Contras) just wanted to intimidate, because the shots they fired weren't aimed directly at the soldiers," said a witness who was passing in his truck when the attack occurred.

Shell casings and bullets were strewn on the highway after the attack, he said.

The U.S.-trained and funded Contras fought a nine-year war against the leftist Sandinista government that ruled Nicaragua from 1979 to 1990.

The 22,000 Contras laid down their arms in return for promises of farmland, homes, and financial help. But one year after Chamorro assumed office many former Contras accuse her government of not following through on the promises.