The bus travelling from the capital, Maputo, to the second city of Beira was ambushed from the front and side, the first such attack on a civilian vehicle in the war-scarred southern African nation in a decade, the O Pais newspaper said.
The attack came two days after militiamen loyal to the opposition Renamo party attacked a police station in Muxungue, killing four policemen in a bid to free more than a dozen colleagues arrested the previous day in a police raid on their party headquarters.
Renamo security chief Osufo Madate denied any Renamo involvement in the bus attack, which rekindled memories of the violence common in a 16-year, post-independence civil war that ended in the early 1990s.
Political tensions in the mineral-rich former Portuguese colony have been rising since police killed two men when they stormed Renamo offices in a northern town a year ago.
Renamo president Afonso Dhlakama briefly retreated to a camp in the secluded Gorongosa Mountains in November, threatening to set up a guerrilla training camp and kick off another war against the ruling Frelimo party.
Although resumption of full hostilities is unlikely given Frelimo’s political and military dominance since a shaky 1992 truce, tensions are bound to worry the foreign mining firms exploring some of the world’s largest untapped coal and natural gas reserves.
Major investors include Italy’s Eni, New York-listed Anadarko, Brazil’s Vale and London-listed Rio Tinto.
Mozambique’s offshore Rovuma gas field is believed to hold 150 trillion cubic feet of gas, enough to supply Germany, Britain, France and Italy for 15 years.