Singapore: London copper futures rose for a sixth session in a row on Friday in their longest winning run this year, backed by tighter physical supply in top metal consumer China.

Other base metals climbed with copper, joining a rally in global equities while gold held onto most its gains from Thursday when it surged the most in nine months.

China's copper imports are likely to fall as an ongoing probe in Qingdao port into alleged fraudulent use of the metal as a collateral for loans has prompted banks to be stricter in lending to trading companies, analysts said.

Physical copper supply in China is tightening at a time when demand is brisk, boosting premiums for the metal in Shanghai.

Supply shortage is also supporting zinc, with London futures scaling a fresh 16-month high and heading for their largest weekly increase this year.

Three-month copper on the London Metal Exchange was up 0.9 percent at $6,782 a tonne by 0711 GMT, after peaking at $6,794 earlier, its loftiest since June 5.

Friday marked the sixth straight day of gains for copper, its longest winning streak since a seven-day rise in December.

For the week, copper was up 1.9 percent, its biggest weekly increase since late March.

Premium for physical copper in Shanghai surged to 580-730 ($93-120) yuan per tonne over the Shanghai front-month futures on Friday from a small discount last week, said Guo Hao, analyst at Jinrui Futures in Shenzhen, suggesting tight supplies.

"We think demand is one reason. It's very hot right now and sales of airconditioning units are rising," said Guo. Hot temperatures typically lead to higher demand for copper tube that is used in air conditioners.

"Also because of the Qingdao probe, copper imports are depressed as banks are making it more difficult for trading companies to secure letters of credit," Guo added.

The Chinese port, the world's seventh busiest, has been at the centre of a probe looking into whether a private metals trading firm, Decheng Mining, used multiple warehouse receipts for the same metal cargo to obtain financing.

ZINC JUMPS Copper's upside potential may be capped in the months ahead with seasonal demand soon tapering off, said Guo, who sees the metal trading between $6,600 and $7,000 between now and August.

The most-traded August copper contract on the Shanghai Futures Exchange rose 1.4 percent to close at 48,760 yuan a tonne.

LME zinc, which hit an intraday top of $2,175 per tonne - its highest level since Feb. 18, 2013, was trading up 0.8 percent at $2,171 and has gained nearly 4 percent for the week. It was zinc's largest weekly rise since August last year.

Global zinc demand outpaced supply by 107,000 tonnes in January to April, up sharply from a deficit of 17,000 tonnes in January-March, data from Lisbon-based International Lead and Zinc Study Group showed on Monday.

Zinc stocks on LME warehouses have been falling this year hitting 674,375 tonnes on Wednesday, the lowest since late 2010 {MZN-STOCKS}. While lead stocks were similarly low, prices have not risen as sharply.

"The difference appears to be that participants are still engaged with zinc, while lead remains in the shadows with prices remaining rangebound," Standard Bank said in a note.

"The resulting lack of volatility in lead is in turn seeing participants look for metals with a more of a story or with some technical momentum at least, with lead falling even further out of favour," it added.

($1 = 6.2090 Chinese Yuan Renminbi)