Amazon is reportedly closing in on a deal to buy the ad-serving technology of bankrupt ad tech firm Sizmek as it looks to mount a serious challenge to the advertising duopoly of Google and Facebook.

According to Bloomberg, citing a pair of sources, the agreement could be announced sooner rather than later, though a deal is yet to be finalised.

Sizmek filed for voluntary bankruptcy in US at backend of March, in order to protect its value in the face of owing between 1,000 and 5,000 creditors money. The company placed an estimate valuation of between $100m and $500m on its assets.

The bankrupt company has already sold some of its assets to Zeta Global Holdings for about $36m. Under that deal, which closed at the beginning of this month, Zeta added Sizmek’s demand side platform (DSP) and data management platform (DMP) to its product portfolio, while hiring more than 200 of Sizmek’s employees.

Sizmek’s ad server helps advertisers place spots online and measure their effectiveness. It competes with the Google Marketing Platform, which was previously known as Doubleclick.

According to eMarketer, Google will account for 31.1 per cent of the worldwide digital ad market this year, while Facebook (including Instagram) will grab a 20.2 per cent of the global market.