LONDON (Reuters) - The main share index rose almost 1 percent by midday on Friday, buoyed by banking and mining sectors, and volumes remained low ahead of U.S. jobs data.

At 11:39 a.m., the FTSE 100 <.FTSE> was up 51.7 points, or 0.9 percent, at 6,139.0. The benchmark index gained 6.8 percent in April, its best monthly performance in five years.

Among gainers on Friday, Rio Tinto (Frankfurt: 855018 - news) <RIO.L>, which has rejected a bid from rival BHP Billiton (LSE: BLT.L - news) <BLT.L>, climbed 0.8 percent after the company's Chairman Paul Skinner was quoted by the Sydney Morning Herald as saying that a break-up of Rio Tinto was an option to extract the best possible return for shareholders.

BHP advanced 1.2 percent, while Kazakhmys (LSE: KAZ.L - news) <KAZ.L>, Lonmin (LSE: LMI.L - news) <LMI.L>, Vedanta Resources (LSE: VED.L - news) <VED.L>, Xstrata <XTA.L> and Eurasian Natural Resources <ENRC.L> were up 1.3 to 3.3 percent.

U.S. stocks rose overnight as a rebound in the dollar and retreating oil prices calmed fears about inflation. In Asia, Japan's Nikkei (news) average <.N225> rose 2.1 percent.

Investors will focus on the U.S. non-farm payrolls data due at 1230 GMT for further clues on the state of the world's largest economy. Economists in a Reuters survey forecast 80,000 jobs were lost in April, a repeat of the March figure.

"We have to be quite cautious ahead of the non-farms," said Mark Priest, a senior trader at TradIndex. "Part of all this recession and concerns over the economy, employment is key factor and if they come in weaker or stronger than expected, we will see markets shoot one way or another."

Banks were another standout sector, with Royal Bank of Scotland (LSE: 91ID.L - news) , HBOS <HBOS.L>, Lloyds TSB <LLOY.L>, Alliance & Leicester <ALLL.L>, Standard Chartered (LSE: STAN.L - news) <STAN.L> and Barclays (LSE: BARC.L - news) <BARC.L> rising between 1 and 2.8 percent.

The Daily Telegraph said Texas Pacific Group was poised to bid for RBS (LSE: RBS.L - news) ' insurance arm. RBS said last month it would consider selling off all or part of its insurance arm as part of efforts to strengthen its capital ratios.

Insurers were also in demand. The Financial Times said Germany's Allianz <ALVG.DE> could make a big acquisition in the general insurance market and was gearing up for a possible assault on UK life assurance by importing U.S.-style retirement savings products to Britain. Allianz was not immediately available for comment.

Aviva <AV.L>, Standard Life (LSE: SL.L - news) <SL.L>, Prudential <PRU.L> and Friends Provident (LSE: FP.L - news) <FP.L> and Admiral <ADML.L> were up 2.3 to 4.1 percent.

Retailers also supported the index, with Next <NXT.L> and Marks & Spencer <MKS.L> riding high on a bear squeeze, traders said.

"The volumes aren't good. It's a long bank holiday weekend," said one London trader in retailers. "Whether we get a dose of reality with the payrolls this afternoon I don't know but there is a lack of volume here."

Building materials distributor Wolseley (LSE: WOS.L - news) <WOS.L>, which earns half of its revenue in North America, rebounded 4.1 percent after a recent battering.

John Wood Group (LSE: WG.L - news) <WG.L> and British Energy (LSE: BGY.L - news) <BGY.L>, however, were down.

Shares in Cadbury <CBRY.L> fell 1 percent on their first day of trading as a standalone confectionery group, undermined by the prospects for its soon-to-be spun off North American Dr Pepper drinks arm.

(Additional reporting by Dominic Lau; Editing by Erica Billingham)