Twitter on Tuesday said it will buy Indian mobile phone marketing start-up ZipDial, as the microblogging service looks to expand in the world's second-biggest mobile market. ZipDial gives clients phone numbers for use in marketing campaigns. Consumers call the numbers and hang up before connecting and incurring charges, and then receive promotion-related text messages.

Twitter did not disclose terms of the purchase. Techcrunch, citing unidentified sources, reported the deal at $30 million to $40 million.

"This acquisition significantly increases our investment in India, one of the countries where we're seeing great growth," Twitter said in a statement.