* Chinese steel producers have cut prices in response to weaker yuan
* Disruptions in iron ore flow from Tianjin port after explosions
* BHP says working with customers after Tianjin ops disrupted (Adds BHP Billiton's comment on Tianjin, updates prices)
By Manolo Serapio Jr
MANILA, Aug 13 (Reuters) - Iron ore futures in China jumped nearly 4 percent on Thursday to their highest in more than five weeks, extending recent gains on hopes stronger steel exports from China due to a weaker yuan would support demand for the raw material.
Also aiding sentiment, the flow of iron ore stocked at China's northeastern Tianjin port has been disrupted, according to traders and global miner BHP Billiton (LONDON:BLT) BHP.AX , following two massive explosions.
Chinese steel producers have already cut export prices in response to a lower yuan, industry sources said, providing some of the first evidence of how Beijing's devaluation will help companies in the world's second-biggest economy boost sales.
Iron ore for January delivery on the Dalian Commodity Exchange climbed as far as 3.9 percent to hit the exchange-set ceiling of 388.50 yuan ($61) a tonne, the highest since July 6. It closed up 3.6 percent at 387.50 yuan.
Iron ore futures on the exchange, the world's most liquid derivatives market for the steelmaking raw material, have been gaining this week after China's surprise devaluation of the yuan, which critics see as Beijing's bid to boost exports.
Falling domestic demand has fuelled steel exports from the country, with shipments in July reaching 9.73 million tonnes, near the record high of 10.29 million tonnes in January.
"While the decision to weaken the renminbi was seen as a one-off, policymakers and central bankers still have a number of options available as they try in vain to kick-start the Chinese economy," Sucden Financial analyst Kash Kamal said in a note.
"Further intervention and capital support could in turn shore up spot iron ore prices."
Iron ore for immediate delivery to the Tianjin port was little changed at $55.80 a tonne on Wednesday, according to The Steel Index. The spot benchmark hit a one-month high of $56.40 last week.
A cargo of global miner Rio Tinto (LONDON:RIO)'s 61-percent grade Pilbara iron ore fines was sold at $55.61 a tonne in a tender on Wednesday, traders said, largely in line with last week's sales of the same grade.
In Tianjin, the explosions that killed at least 44 people, including at least a dozen firefighters, have restricted transport of iron ore stocks at the port, said a Shanghai-based trader.
Operations at the north and south parts of the port have been temporarily stopped, he said, citing information received from authorities probing the blasts. About 7 million tonnes of iron ore are stored at these parts of the Tianjin port, he said.
"There's a lot of floating articles in the air and transportation has been restricted. If you want to take delivery from the port, you will be affected," he said.
BHP said shipments and port operations have been disrupted and that it was working with clients to minimise any potential impact.
A Tianjin port official said the port is operating normally.
Rebar and iron ore prices at 0707 GMT
Contract
Last
Change Pct Change SHFE REBAR JAN6
2092
+31.00
+1.50 DALIAN IRON ORE DCE DCIO JAN6
387.5
+13.50
+3.61 SGX IRON ORE FUTURES SEP
52.7
+1.26
+2.45 THE STEEL INDEX 62 PCT INDEX
55.8
-0.10
-0.18 METAL BULLETIN INDEX
56.31
+0.09
+0.16
Dalian iron ore and Shanghai rebar in yuan/tonne Index in dollars/tonne, show close for the previous trading day ($1 = 6.4150 Chinese yuan)