Federal Reserve Chair Janet Yellen boosted Wall Street Friday, restating her confidence in the US economy but softening her view on interest rate hikes after a poor US employment report.

Meanwhile London stocks rallied despite new polls that put the British referendum vote back on a knife-edge and sent the pound tumbling.

Yellen helped markets tentatively put last Friday's surprisingly dismal US jobs report behind them, saying one month's data is not so significant and that the overall labor market situation has been "quite positive".

But she backed away from previous Fed hints for a rate increase in June or July, only saying that tighter monetary policy should come gradually.

That helped the S&P 500 to a seven-month high with a 0.5 percent gain for the day.

US and London stocks were also boosted by a surge in crude prices as Nigerian production remains under pressure from militant attacks, and general support for commodities from the lower dollar.

The FTSE 100 gained 1.0 percent, outpacing rival Frankfurt and Paris markets.

"Commodity stocks are continuing to benefit from Friday's sharp drop in the US dollar, which along with noises from the US about China reducing its excess steel capacity as part of a bilateral trade agreement, is supporting a rise in metals prices," said CMC Markets analyst Jasper Lawler.

Shares in miner Anglo American were the biggest gainer on the FTSE 100, jumping 11.1 percent.

ConocoPhillips added 3.0 percent and Exxon Mobil 1.1 percent; BP rose 2.0 percent and Total 1.3 percent.

But a fresh surge in sentiment for Britain exiting the European Union, with the June 23 referendum approaching, pushed Britain's currency to around three-week lows against the euro and dollar, before rebounding.

The euro hit 79.05 pence in Asian trading hours -- the European single currency's highest level against sterling since mid-May. But in late trade it was about 78.64 pence.

Against the greenback, the pound slid to $1.4353, a three-week low, before recovering to $1.4439.

"The polls are having a significant impact on the pound," said Craig Erlam, senior market analyst at Oanda trading group.

A strong yen meanwhile continued to hit Japanese exporters -- resulting in Tokyo's Nikkei stocks index ending the day lower.

- Key figures at 1900 GMT -

New York - Dow: UP 0.6 percent at 17,920.33 (close)

New York - S&P 500: UP 0.5 percent at 2,109.41 (close)

New York - Nasdaq: UP 0.5 percent at 4,968.71 (close)

London - FTSE 100: UP 1.0 percent at 6,273.40 (close)

Frankfurt - DAX 30: UP 0.2 percent at 10,121.08 (close)

Paris - CAC 40: UP 0.04 percent at 4,423.38 (close)

EURO STOXX 50: UP 0.2 percent at 3,001.90 (close)

Tokyo - Nikkei 225: DOWN 0.4 percent at 16,580.03 (close)

Shanghai - Composite: DOWN 0.2 percent at 2,934.10 (close)

Hong Kong - Hang Seng: UP 0.4 percent at 21,030.22 (close)

Euro/dollar: DOWN at $1.1355 from $1.1364 late Friday

Dollar/yen: UP at 107.57 yen from 106.63 yen

Pound/dollar: DOWN at $1.4439 from $1.4517

Euro/pound: UP at 78.64 pence from 78.28 pence