Pope Francis on Sunday condemned the killing last week of an environmental activist in Honduras who had protested over mining and hydro-electric projects to try to protect tropical forests and rivers.

Juan Lopez was shot dead by several men as he headed home in his car from church, an official told Reuters, speaking on condition of anonymity.

Lopez belonged to the Municipal Committee for the Defense of Common and Public Goods, an environmental organization in the city of Tocoa close to the country's Atlantic coast and was also an active member of the local church.

"I join the mourning of that church and the condemnation of all forms of violence," Francis said at the end of his Angelus message at the Vatican.

"I stand with those who see their basic rights trampled and with those who act for the common good in response to the cries from the poor of the earth," he added.

The pope has repeatedly spoken out on environmental issues, saying last month that the earth was sick, and urging people to do more to protect it.