Ukraine on Wednesday escalated its bitter trade war with Russia in punishment for Moscow's seeming efforts to choke off its westward-leaning neighbor’s economic ties with other former Soviet states.

Prime Minister Arseniy Yatsenyuk told a cabinet meeting that Kiev was adding 70 food products to its existing list of items Russia cannot sell in Ukraine.

Chinese President Xi Jinping and Saudi King Salman on Wednesday attended a ceremony to mark the opening of a joint-venture refinery, a symbol of Beijing's deepening involvement in the Middle East.

The event took place in the Saudi capital Riyadh on the second day of Xi's first visit to the region. He was to depart later in the day for Egypt and will also travel to Saudi Arabia's rival Iran.

Falling world oil prices combined with a fixed fee for the use of export pipelines mean South Sudan is now losing money on every barrel it sells, analysts said Wednesday.

South Sudan currently earns around $20 (18 euros) a barrel for its low quality oil that sells at a discount to the Brent crude benchmark -- on Wednesday trading at $28 (26 euros), said Emma Vickers of Global Witness, a London-based campaign group.

The ruble fell close to a historic low on Wednesday, as the dollar climbed past the psychological threshold of 80 rubles for the first time since the shock plunge of the Russian currency in December 2014.

After a day of relative calm, the ruble continued on a downward spiral, falling to 80.01 against the dollar, just eight kopecks away from the historic low of December 2014, as oil prices, key to Russia's economy, were testing 12-year lows.

The tide of Middle East refugees should boost European economic growth over the short term, but their longer-term impact will depend on efforts to integrate them, the IMF said Wednesday.

In a new study to be presented at the World Economic Forum in Davos, Switzerland this week, the International Monetary Fund said that governments making strong efforts to bring refugees into the workforce can lessen the chance that they will become a burden on the state budget.

Rising risks to the global economy and a string of jihadist attacks around the world overshadowed Wednesday's opening of an annual meeting of the rich and powerful in a snow-blanketed Swiss ski resort.

The Taliban assault on a university in Pakistan that left at least 21 dead was a jolt to the billionaires, business titans and leaders, including Pakistani Prime Minister Nawaz Sharif, gathering in the Swiss Alpine village of Davos.

An Italian construction group said Tuesday it had signed a preliminary agreement with Iran to build five hospitals, just after the lifting of economic sanctions against Tehran in a deal over its nuclear program.

Pessina Costruzioni will build the first three 1,000-bed hospitals in Tehran.

U.S. crude prices extended losses Wednesday, heading towards $27 a barrel, as the International Energy Agency (IEA) warned that the oil market could "drown in oversupply".

West Texas Intermediate (WTI), the U.S. benchmark, fell to levels last seen in September 2003, touching $27.49 at one point.

Adidas' incoming chief Kasper Rorsted faces major challenges when he takes over as the global sports brand's new CEO later this year as the company struggles to catch up with arch-rival Nike, analysts said.

Investors feted the announcement on Monday that Adidas had successfully poached the 53-year-old Dane from consumer chemicals giant Henkel, with the group's shares the biggest gainers on the Frankfurt stock exchange. 

Cobalt mined dangerously by children in the Democratic Republic of Congo could end up in the lithium batteries of smartphones and electric cars made by Apple, Samsung or Sony, Amnesty International said Tuesday.

After questioning 16 multinationals, the human rights watchdog said world-class electronics brands are failing to ensure that no child miners were involved in lithium-ion batteries used in their products, according to a joint report released with Afrewatch.