Prime Minister Justin Trudeau says Canada is looking at ways to do more to help South Sudan, where millions face famine.

Earlier this week, senior clerics from three of Canada's largest denominations issued an open letter asking the federal Liberal government to increase aid to the country and encourage other countries to do more.

They say hunger is stalking 20 million people in South Sudan, as well as Yemen, Somalia and Nigeria.

South Sudan gained independence from Sudan in 2011, after years of brutal fighting, but civil war broke out again in 2013 as the new government was riven by ethnic divisions.

The fighting has coincided with famine in the landlocked, northeastern African country.

Trudeau says the country has already made major contributions.

"Canada ... has been a significant donor in terms of international aid to South Sudan over a number of years and we're always looking for ways to do more," he told a news conference Friday.

Ensuring help gets to the neediest

International Development Minister Marie-Claude Bibeau said Canada has already provided almost $37 million to South Sudan this year. A total of $119 million has been earmarked for South Sudan, Yemen, Somalia and Nigeria.

She said the factions fighting in South Sudan must help ensure access to the neediest people in the country.

"We are calling on all the parties to open and give access to humanitarian workers, because we do have access to a certain number of the most vulnerable, but there are some we cannot reach."

Bibeau and Trudeau were in Montreal to announce the headquarters for Canada's new Development Finance Institute, aimed at facilitating economic growth partnerships with small and medium private-sector enterprises.

Hustin Laku, a researcher at the University of Juba, discusses the dire situation and how the country got to where it is now 7:37

The institute's mandate is to promote inclusive green economic growth in the developing world, while promoting the involvement of women and young entrepreneurs in achieving sustainable development objectives.

Bishop Douglas Crosby of the Canadian Conference of Catholic Bishops, Archbishop Fred Hiltz of the Anglican Church of Canada and Rev. Douglas Rollwage of the Presbyterian Church in Canada warned in their open letter that both sides in South Sudan are committing atrocities.

"We are continuing to hear disturbing reports of gross violations of fundamental human rights being carried out with total impunity," the letter said.