KazMunaiGas, Kazakhstan's state oil and gas company, secured a $1.13 billion Chinese loan on Wednesday to complete an upgrade that will enable its Atyrau oil refinery to produce cleaner fuels.

The loan from China's Export-Import Bank will be repayable over 13.5 years, KazMunaiGas said.

The loan will finance a large part of a $1.68 billion project to build a new facility at Atyrau, Kazakhstan's oldest refinery, which will be capable of processing 2.4 million tonnes per year of fuel oil and vacuum gas oil.

"The new complex will allow us to increase production of high-octane gasoline, jet fuel and diesel that will meet Euro-5 emissions standards," Talgat Baitaziyev, general director of the Atyrau refinery, said in a statement.

Kazakhstan, which holds 3 percent of the world's recoverable oil reserves, has doubled crude production over the past decade to become the second-biggest producer in the former Soviet Union after Russia.

The country has three refineries, two of which are owned by KazMunaiGas. Ownership of the third refinery, Shymkent, is shared between KazMunaiGas and China National Petroleum Corp.

China has invested around $15 billion into Kazakhstan, roughly a tenth of the total foreign investment attracted by the former Soviet republic since independence in 1991. Most of this investment has been in the past few years.

"In the crisis years, our companies received access to Chinese investment in the region of $10 billion," Kazakh President Nursultan Nazarbayev said in comments published on the presidential website, www.akorda.kz.

Around 20 percent of Kazakhstan's oil and gas exports are destined for China, Nazarbayev said.

Nazarbayev, along with other Central Asian leaders and Russian President Vladimir Putin, was in Beijing for a meeting of the Shanghai Cooperation Organisation regional security forum.

Annual trade turnover between China and Kazakhstan is around $25 billion, Nazarbayev said. Official data show Kazakhstan exported goods worth more than $16 billion to its neighbour last year, more than 18 percent of its total export revenues.

Chinese company Sinopec Engineering is overseeing the Atyrau deep refining project as part of a consortium that also includes Japan's Marubeni Corp and Kazakh firm KazStroiServis. The facility is scheduled for completion in 2015.