By Sarah Turner

LONDON (Dow Jones)--Most oil and gas firms advanced in a flat London market on Wednesday with BP shares higher after the firm said it has made a major oil discovery in the Gulf of Mexico.

BP (BP) said it drilled to one of the deepest depths ever in the oil and gas industry as it touted a "giant" discovery off the coast of Texas, while adding that it has yet to assess the amount of oil available there. The stock rose 4.3%.

At the Tiber prospect, BP said it drilled to a total depth of roughly 35,000 feet to reach the oil. The site is 250 miles southeast of Houston in 4,132 feet of water.

Other oil and gas firms on the move included natural-gas producer BG Group , up 1.8%, and Royal Dutch Shell (RDSA), up 1.1%.

The move in the oil and gas sector helped to offset weak financial and mining stocks, allowing the FTSE 100 index to close virtually unchanged at 4,817.55.

The index finished down 1.8% on Tuesday.

Other European shares ended on Wednesday. U.S. stocks turned higher mid-morning.

Banks were some of the worst performers in London, with shares of Royal Bank of Scotland down 4%, shares of Lloyds Banking Group (LYG) down 6.2% and Barclays (BCS) shares down 3%.

Metal extractors were also lower, with Rio Tinto (RTP) shares down 0.8% and Antofagasta shares down 3.3%.

Both sectors have rallied sharply since shares in the U.K. hit multi-year lows in March as investors hoped the economic backdrop was set to improve.

On Wednesday investors were buying up some stocks that are normally regarded as safe-haven places for investors to put their money, such as food retailers and tobacco firms.

Shares of supermarket group William Morrison rose 3.6% and Tesco shares were up 1%.

Merrill Lynch analysts said that they rate both firms at buy.

"Inelasticity of demand and concerns of falling food inflation have weighed on the food retailers' share performance. This looks a little overdone with the sector trading slightly below its long-run market-relative rating," the analysts said.

It reinstated coverage on 10 general retail stocks in Europe, also rating Home Retail , Kingfisher and Next at buy.

"We think there is a margin story as surplus capacity and retailer flexibility has reduced the dollar sourcing drag; and as cost-cutting, lower rent costs and extra volume have leveraged profit and loss accounts," the broker said.

Home Retail shares rose 0.6%, Kingfisher shares climbed 0.8% and Next shares were up 1.4%.

DSG International shares climbed 2.7% outside the top index.

On Wednesday, the firm posted a 6% drop in 16-week comparable sales, although it said that this was a better result than analysts had been expecting.

Margins increased 0.7% year-on-year, the firm added.

-Sarah Turner; 415-439-6400; AskNewswires@dowjones.com