* Oil back below $30 after brief Thursday reprieve
* European stocks fall 1.2 percent, Asia shares hit 3-1/2-year low
* Commodity currencies face fresh beating with sentiment frail
* Aussie dollar hits 7-year low, Canadian dollar at 13-year low
By Dhara Ranasinghe
LONDON, Jan 15 (Reuters) - World stocks were set for a third straight week of losses on Friday and commodity currencies took another drubbing as oil prices fell back below $30, keeping alive concerns about global growth.
European stocks .FTEU3 fell more than 1 percent, heading back towards Thursday's 13-month lows, while Asian shares skidded to 3-1/2 year lows .MIAPJ0000PUS .
Oil prices, which posted their first significant gains for 2016 on Thursday, came under fresh selling pressure as the prospect of additional Iranian supply loomed over the market.
Brent crude LCOc1 fell 3 percent to $29.86, heading for a weekly loss of more than 10 percent. U.S. crude fared even worse, sliding almost 5 percent to $29.75, and was set for a weekly decline of 10 percent.
The collapse in oil prices has spooked financial markets as investors worry about the health of the global economy, with a slowdown in China and volatility in its markets making for a nervous start to the year.
"It's been another immensely volatile week," said Philip Shaw, chief economist at Investec in London.
The Shanghai Composite .SSEC lost 3.5 percent, while the CSI300 .CSI300 tumbled 3.2 percent. That put the former on track for a 9 percent loss for the week, and the latter for a decline of 7.2 percent.
Chinese shares extended their losses after data showed new yuan loans in December were well below the previous month's lending, and broad M2 money supply growth also slowed, with both missing expectations. will publish a host of data on Monday and Tuesday, including fourth quarter gross domestic product. ECONCN
U.S. retail sales data due later on Friday will also be on investors' radar as they try to gauge the likelihood of the Federal Reserve raising interest rates again in March.
FEELING THE PAIN
The combination of sliding oil prices and China concerns delivered another knock to commodity-linked currencies.
The Canadian dollar fell to C$1.4521 against its U.S. counterpart CAD= , its lowest level since early 2003, while the Australian dollar fell to a seven-year low at $0.6880 AUD=D4 .
The U.S. dollar was weaker against the euro and the yen, helping push the dollar index . DXY down 0.18 percent to 98.895.
"It's another risk-off day," said Chris Scicluna, head of economic research at Daiwa Capital Markets. "We had an awful session in Asia and that has spilt over into Europe."
Worries that a depreciating Chinese yuan could spark competitive currency devaluations across the region have also hit global shares this month.
On Friday, the yuan CNY=CFXS , posted modest gains. That put the Chinese currency 0.1 percent up on the week, but it was still around 1.4 percent weaker against the dollar than it started the year and has lost nearly 5 percent since August.
The People's Bank of China set a marginally weaker midpoint of 6.5637 CNY=SAEC . The spot market CNY=CFXS opened at 6.5920 per dollar and was changing hands at 6.5858 at 0935 GMT.