Palantir Technologies, the secretive data firm that works with military and law enforcement, has raised $679 million in funding, confirming its status as one of the richest tech startups.

The Silicon Valley company, whose predictive analytics technology was reportedly used by the US military to track down Osama bin Laden, disclosed the latest funding in a filing this week with the Securities and Exchange Commission.

Palantir's valuation has been estimated by analysts at $20 billion, making it the biggest venture-backed firm in the US after Uber and Airbnb. It was not immediately clear if the valuation changed with the latest funding.

While Palantir keeps largely away from the public spotlight, media reports say its data analytics technology is used for military, intelligence and law enforcement.

It also works in areas such as disaster relief, fraud detection, tracking supply chains and dealing with economic upheaval.

Its early funders include In-Q-Tel, the venture capital arm of the CIA.