LONDON - A JPMorgan Chase & Co vehicle on Wednesday increased its cash offer for London-listed carbon offset aggregator EcoSecurities, garnering further support from shareholders.

Carbon Acquisition Company said it had increased its recommended offer to 105 pence per share, valuing EcoSecurities at some 129 million pounds ($211 million), and bought a further 18.3 million EcoSecurities shares, or almost 15.5 percent of the company.

The new offer compares with JP Morgan's previous bid of 100 pence and a rebuffed offer of 90 pence from rival bidder Pedro Moura Costa, the co-founder and former president of EcoSecurities.

EcoSecurities in a brief statement recommended shareholders accept the revised JP Morgan offer.

It's slightly unusual to outbid yourself without the other party intervening but it's likely 105 pence was the price they had to pay on market to acquire the additional shares, said analyst Ken Rumph at Nomura Code.

Analyst Gus Hochschild at Mirabaud, however, said the increased offer was in response to market expectations that Guanabara would make a counterbid.

Costa's investment vehicle, Guanabara, said last week it was extending its offer for EcoSecurities and that it reserved the right to increase its offer further now that a bidding war had broken out.

Guanabara's advisors declined to comment on the JP Morgan statement and when contacted by Reuters on Wednesday, Costa said his position had not changed since last week's statement.

We are in the process of due diligence to decide on a potential revised offer, he said via telephone.

Including acceptances from shareholders owning 19.9 percent of the firm, JP Morgan now owns or has agreed to acquire 35.9 percent of EcoSecurities.

The door is still open for Guanabara, Nomura's Rumph added. Thirty-five percent still isn't more than fifty percent.

At 0811 GMT, shares in AIM-listed EcoSecurities were up 2.4 percent at 105.6 pence.

(Reporting by Victoria Bryan; Editing by Rhys Jones and Rupert Winchester)

($1=.6121 Pound)