Facebook founder Mark Zuckerberg and his wife Priscilla Chan have been named joint top US philanthropists for 2013.

The couple gained the accolade after a donation of 18 million Facebook shares to a Silicon Valley foundation.

The donation, worth more than $970 million (Rs 6,005 crore), was the largest in the US in 2013.

The gift outstripped philanthropists such as Bill and Melinda Gates.