By Sinead Cruise, Kirstin Ridley and Samuel Indyk

LONDON (Reuters) – Anglo American's London-listed shares spiked in late UK trade on Wednesday, hours before the miner announced a $39 billion bid by rival BHP Group, raising questions from some lawyers, investors and commentators about possible leaks.

Shares in Anglo rose by around 2.8% between 1500 GMT and the market close at 1530 GMT in London on Wednesday. Anglo issued a statement around 2300 GMT saying it had received an approach from BHP.

The late bounce before the bid proposal was revealed, which if successful would forge the world's biggest copper miner, contrasted with modest share price gains of between 0.2-0.5% at Anglo's peers Rio Tinto, Glencore and Antofagasta in the 35 minutes before the London market closed.

"This spike in Anglo's share price before the public announcement of the BHP bid raises questions about the integrity of the UK's markets which the Financial Conduct Authority (FCA) are likely to want to investigate," said Harvey Knight, head of the financial services regulatory group at law firm Withers LLP.

Britain's FCA does not typically comment on individual trading irregularities which it investigates and declined to comment on whether it would review the activity.

In a statement emailed to Reuters, the regulator said it "cannot comment on individual cases".

A spokesperson for Anglo American declined to comment when asked whether the company had contacted the FCA about any potential irregular trading or whether the regulator had been in touch.

"The price spiked significantly. Someone was either very lucky or very knowledgeable," said Richard Bernstein, chief investment officer of activist investor Crystal Amber.

Shares in miners like Anglo can move sharply following changes in commodity prices, or major currencies like sterling and the U.S. dollar.

Regulated companies and individuals in Britain have an obligation to detect and report suspicious trading if there are reasonable grounds to suspect market abuse, such as insider dealing or market manipulation.

"Between private chat networks, secure texting apps, and even burner phones, there are many more ways for material, non-public information to be shared via undetected means than there ever were previously," Peter C. Earle, Senior Economist, The American Institute for Economic Research, told Reuters.

"The financial markets are in an information dissemination arms race. Some of it is above board, and some of it below."

(Reporting By Sinead Cruise, Kirstin Ridley and Samuel Indyk; Additional reporting by Amanda Cooper and Nell Mackenzie Editing by Elisa Martinuzzi and Elaine Hardcastle)