LONDON, July 15 (Reuters) - Britain's financial regulator said on Wednesday it was keeping an eye on an approach by investment firm Litani to some shareholders in London-listed insurer Aviva AV.L.

Nikhil Rathi, the chief executive of the Financial Conduct Authority, told lawmakers on the Treasury Committee that the regulator would assess whether the law was being followed and ensure any communications to shareholders was fair and clear.

Aviva has urged shareholders to reject a "mini-tender" by Litani for their shares at 17.5% below the market price.

"Offers like this, sometimes called 'mini-tender offers', typically involve buying shares at a lower price and then selling them on at the full market price, allowing the buyer to make a profit at shareholders' expense," the insurer said in an undated message posted on its website.