LONDON/FRANKFURT, May 28 (Reuters) - Uber has raised its stake in Germany's Delivery Hero to nearly 37% from 25% after buying a stake from fellow shareholder Aspex Management, according to regulatory filings and two people close to the matter.

The deal with Aspex comes as Uber is working on a new bid to take over the German food delivery company following an indicative €33-per-share ($38.29) proposal on Saturday, two separate sources said on Thursday, speaking on condition of anonymity because the talks are private.

Delivery Hero declined to comment.

Uber did not immediately respond to a request for comment.

Shares in Delivery Hero fell 3.6% to €37.93 per share by 0751 GMT. 

Uber now holds a total of 36.83% in Delivery Hero - 24.99% in common shares and the rest linked to derivative instruments - compared with 25.1% previously, the filings in Germany published late on Wednesday show.

A separate regulatory filing showed Aspex has almost halved its stake to 7.56% from 14.55%, while the remaining stake will be transferred at a later date.

Delivery Hero confirmed on Saturday it had received an indicative proposal from Uber valuing the company at €33 per share. The German group's CEO Niklas Oestberg said last week he would step down, following campaigns by several large shareholders for a strategic review.

The FT had reported that Uber's board met on Saturday to discuss raising its offer after its initial approach was rebuffed.