(CNN) -- At least four people died and 27 were wounded in riots that erupted Wednesday after Mozambique's government announced increases in the price of bread, water, energy and other critical goods, the southern African nation's official news agency reported.
The exact death toll was unclear -- the news agency said other "credible sources" were reporting at least 10 people had died.
And a U.S. Embassy official in the capital city, Maputo, told CNN that credible sources were citing six deaths, including a child. He said that two secondary-school students were among the injured.
Police made 142 arrests, according to police spokesman Pedro Cossa, who said casualty figures were likely to rise.
Cossa said police used tear gas and rubber bullets against the rioters, but local media -- citing witnesses -- said real bullets were also used.
Three buses were burned, 32 shops were vandalized and more than five cars were burned or vandalized, Cossa added.
The price hikes are to go into effect September 6.
The violence took place in the cities of Maputo and Matola, with the deaths occurring on the outskirts of Maputo, the Mozambique News Agency reported.
Bank and electricity company offices were vandalized, and food warehouses belonging to the Sasseka and Delta Trading distribution companies were looted, the report said.
The U.S. Embassy official, who asked not to be identified, said President Armando Guebuza -- in a nationally televised address -- appealed for calm, saying the reputation of the country was at risk, but offering no economic solutions.
He said the government is already subsidizing the prices of food goods and gas.
Minister of Interior Jose Pacheco -- during a news conference -- had called for calm and exhorted parents to control their teenagers.
The U.S. State Department urged American citizens to avoid all unnecessary travel and remain at their homes or hotels until further notice. The embassy will continue to operate, but will provide only emergency American citizen services, it said.
CNN's Jack Maddox contributed to this story.