Russia, which is facing an unprecedented wave of economic sanctions from Western allies over its invasion of Ukraine, accounts for an estimated 10% of global steel trade, while Ukraine has a 4% share, according to Huatai Futures analysts.
The supply interruption will force some major buyers to seek alternative sources, and "currently only China can fill this huge market vacancy", they said in a note.
The most-active May contract for hot-rolled coil - steel used in car bodies and home appliances - on the Shanghai Futures Exchange rose 2.5% to 5,158 yuan ($817.08) a tonne, advancing for a third consecutive day to the highest since Feb. 11.
Shanghai construction steel rebar also climbed 2.5% to hit 4,893 yuan a tonne, the strongest since Feb. 14.
Prospects for increased domestic steel demand also supported prices, analysts said, as China's parliament begins its annual meeting on Saturday and is likely to unveil more stimulus to ease a growth slowdown.
Higher steel prices boosted interest in steelmaking raw materials, with Chinese iron ore and coking coal futures rising by more than 5% in morning trade.
The most-active May iron ore contract on China's Dalian Commodity Exchange surged as much as 5.9% to 764 yuan a tonne, the highest since Feb. 15.
On the Singapore Exchange, iron ore's front-month April contract jumped 1.9% to $150.90 a tonne.
