The Foreign and Commonwealth Office said an exception to the travel advisory was the provincial capital of Beira.
Confrontations between the military and the opposition Renamo party have been reported in the province this month.
"The situation in Sofala province remains tense and ... there were reports of armed attacks in the region," the agency said. "Further attacks can't be ruled out."
Last week, the Renamo movement backed out of a 1992 peace agreement that marked the conclusion of a civil war that erupted after Mozambique gained independence from Portugal in 1975.