OTTAWA -- Canada's foreign aid spending rose slightly in an annual survey of international development spending, but agencies say the increase is underwhelming and are calling on the government to spend more.

The annual ranking by the Paris-based Organization for Economic Co-operation and Development, released Tuesday, said Canada's aid spending rose slightly to 0.28 per cent of Gross National Income in 2015.

That's a slight increase over last year's 0.24 per cent figure, one of the lowest performances by Canada in more than a decade.

The overall international figure was 0.30 per cent, up slightly from the previous year because of global efforts to help the flood of asylum seekers, but still well short of the United Nations goal of 0.7 per cent.

UN Secretary General Ban Ki-moon has urged Canada and all OECD countries to come up with a plan to meet the 0.7 goal, but International Development Minister Marie-Claude Bibeau says that's too ambitious a target for Canada to commit to at the moment.

Canada's modest increase was "mainly due to the timing of contributions to multilateral organizations and humanitarian assistance in response to the ongoing conflict in Syria," the OECD said.

The OECD said the unprecedented flow of 1.5 refugees to its 28-member countries, including more than a million to its European members led to rise in numbers. It said countries can count "certain refugee-related expenses" towards its overseas development spending one year after their arrival.

That helps explain Canada's increase because the country's aid spending has been frozen since 2010. The federal Liberals first budget in February reversed that with a two-year, $256-million commitment aid spending commitment, which came too late to count on this year's OECD report card.

Oxfam Canada and the Canadian Council for International Co-operation separately called the Canadian increase "overstated," and urged the government to come up with a plan to reach the 0.7 target.

"The overall increase is down to the fact that some governments declare costs for receiving refugees in their own countries as development aid," said Brittany Lambert, the senior policy adviser at Oxfam Canada.

"This is aid which never leaves rich countries. While these countries must meet the needs of the refugees and migrants arriving at our borders, it is important this does not come at the cost of aid spending for the world's poorest people."

Gillian Barth, the head of CARE Canada, said any increase is welcome but it important to know that Canada's comes on heels of a near all-time low in spending in 2014. She also called on the Liberals need to find a way to boost the international development envelope closer to the UN target.

"We're looking forward to seeing their mandate for a more proactive and compassionate foreign policy."

OECD Secretary-General Angel Gurria also called on OECD countries to continue increasing foreign aid spending as they grapple with helping refugees on their own soil.

"They also need to develop long-term options for meeting future refugee costs and the integration of refugees in our societies, while ensuring at the same time that ODA reaches those countries and people that need it the most."

Only six countries met or exceeded the UN target in this year's analysis by the OECD's development assistance committee.