Although the two stars have never publicly acknowledged their relationship, reports suggest that the duo exchanged rings over holidays in London on Dec 30.

According to Times of India, a source close to the couple said: "Katrina was in London to celebrate Christmas with her family. Ranbir joined her soon after. In the presence of a few chosen friends and Katrina’s family, the two apparently exchanged rings.”

"The wedding is likely to take place post May this year as work is the couple's priority at the moment," the source added.

However, on Dec 23, Katrina had dismissed all such rumours, saying these were "not true at all".

The article also states that according to a report published on www.bollywoodmantra.com, Ranbir’s parents Neetu and Rishi also flew to London to attend the engagement.

Ranbir, Katrina and Ayan Mukerji reportedly spent the New Year at the Standard Hotel in New York, where singer Rita Ora performed live.

Rumours of Ranbir and Katrina dating have been doing the rounds since the two worked together in Rajkumar Santoshi’s Ajab Prem Ki Ghazab Kahani.

Fans expressed surprise and shock on Twitter: