JOHANNESBURG (Reuters) - German investor ATON said on Thursday it had raised its stake in South Africa's Murray & Roberts (>> Murray & Roberts Holdings Limited) to 33.1 percent as it seeks to takeover the engineering and construction firm despite management opposition.

ATON said after market close it had agreed to buy 13,671,480 ordinary shares in M&R for 15 rand per share. It did not say from whom it had made the purchase. The shares closed at 13.80 rand on Thursday, up 2.2 percent.

It added it had also agreed to buy a further 29,005,926 shares from investment management company Allan Gray, M&R's third largest stakeholder, for 15 rand, which would further raise its stake to 39.6 percent.

M&R previously rejected ATON's buyout offer as "opportunistic" and poor value. M&R is reluctant to sell cheaply, having spent billions of rand transforming itself from a local builder to a multinational focused on the natural resources sector.

ATON said it would be for M&R shareholders to decide on the offer.

Financial services conglomerate Old Mutual, , which holds about 5 percent of M&R, rejected an offer from ATON to buy its stake at 15 rand per share on Wednesday, saying that the offer was below fair value.

ATON, with a diverse portfolio of investments in the mining, engineering, aviation and health technology sectors, is making its second attempt at a deal after a previous approach failed in 2016.

(Reporting by Tanisha Heiberg; Editing by Joe Brock and Alexandra Hudson)

Stocks treated in this article : Murray & Roberts Holdings Limited, Old Mutual