An Air India call centre in Delhi received calls threatening that Mumbai would be "bombed" shortly after the blasts in the national capital, a company spokesman said in Mumbai on Sunday.
"Our call centre in Delhi received two calls yesterday around 7.00 pm. The caller threatened to bomb Mumbai," he told PTI.
"Following the receipt of the call we passed on the information to the city police and also beefed up security at our offices," the spokesman said.
Accordingly, Delhi and Mumbai police and other concerned agencies were informed, he said.
"We have also beefed up security at our establishments," the official added.
Five blasts rocked Delhi's market areas last evening killing 21 people and injuring 97 others.