BEIJING, Sept. 28 (Xinhua) -- The world must stick to multilateralism in order to address various global problems, former Prime Minister of Ireland Bertie Ahern said Friday in Beijing.

Ahern made the remarks when attending the opening ceremony of the 35th Annual Plenary Session of the InterAction Council.

"Global challenges are not confined to borders. They span over regions and continents. They affect us all," said Ahern in his opening remarks to the ceremony, "Global issues require global solutions."

"The international system is currently under attack by protectionism and unilateralism. It is crucial for us to defend the system of international institutions based on treaties and the rule of law," Ahern said.

He was echoed by a group of former world leaders, who spoke to Xinhua after the opening ceremony.

Luis Alberto Lacalle, former president of Uruguay, said multilateral institutions, such as the United Nations and World Trade Organization, have made contributions to global governance and common development in a peaceful manner.

"The international community should be closely united and defend the current global governance system by further cooperation," said Lacalle.

Recalling the scenes when Chinese delegations visited Hungary in the 1970s and 1980s, former Hungarian Prime Minister Megyessy Peter said he was impressed by China's positive attitude in exchanging experiences and cooperating with the world.

China's opening-up policy and its efforts to get involved in economic globalization deserve recognition, Megyessy said. "The improvement of Chinese people's lives and China's contribution to global growth best speak to the importance of cooperation and multilateralism."

Noting that China's Belt & Road Initiative has brought more capital and technology to Africa, a continent that was once "forgotten", former Guinea Prime Minister Kabine Komara said the international community should expand such win-win cooperation and defend multilateralism.

The InterAction Council, an international non-governmental organization composed of some former world leaders, was established in 1983 and aims to put forward suggestions and solutions for global political, economic and social issues. The InterAction Council held its 11th plenary session in Shanghai in 1993, and its 30th plenary session in Tianjin in 2012.