* Energy stocks, miners gain on firmer commodity prices
* Aviva pressured on capital strength concerns, banks lower
* U.S. payrolls data highlights grim economic outlook
By Simon Falush
LONDON, March 6 (Reuters) - Britain's FTSE 100 .FTSE closed flat on Friday, as losses from ailing banks and insurers offset gains in commodity stocks, but the index ended the week in deeply negative territory as U.S. jobs data added to gloom.
The blue-chip index added 0.87 points to close at 3,530.73, after tumbling 3.2 percent on Thursday. It touched a six-year low of 3492.10 earlier in the session and ended the week down 7.8 percent, its fourth consecutive week in the red.
The UK benchmark index is down more than 20 percent so far this year, after sliding more than 31 percent in 2008, and has fallen for each of the last four weeks.
The United States shed another 651,000 jobs in February, in line with expectations, but sharply revised January and December job losses to make them the deepest in 60 years, while the unemployment rate hit a 25-year high of 8.1 percent.
"The market is in a heightened sense of nervousness, sentiment is far from good and there is no obvious end in sight," said Tim Rees fund manager at Insight Investment.
Insurer Aviva (AV.L) shed 14 percent, extending the previous session's 33 percent drop, as analysts cited concerns over the group's capital strength.
Friends Provident (FP.L), Old Mutual (OML.L), Standard Life (SL.L) and Prudential (PRU.L) all sank between 2.2 percent and 5.3 percent.
Banks were mostly lower, but Lloyds Banking Group (LLOY.L) gained 4.2 percent after it said late on Thursday that talks between the bank and the British government over the bank's participation in the toxic asset insurance scheme are still ongoing. [ID:nL5396162]
HSBC (HSBA.L), Barclays (BARC.L) and Royal Bank of Scotland (RBS.L) fell between 1.1 percent and 4.8 percent.
"There's an issue about the amount of capital available for Aviva which has spooked the market and the banks have become an easy target," Gary Thomson, head of sales trading at CMC Markets said.
