A specific alert warning attack by Pakistan-based terrorist group was shared by central security agencies with Hyderabad police on Thursday morning, home ministry officials said on Friday.
Twin blasts ripped through a crowded market in Hyderabad on Thursday, leaving 16 dead and 120 injured.
The ministry had sent specific alert to four cities -- Hyderabad, Bangalore, Coimbatore and Hubli -- warning them of probable attacks by terrorists, they said.
Besides, Maharashtra and Gujarat police forces were also sent the alert, the officials said.
According to home ministry officials, the alerts were also sent to all states on February 19 and 20, that Pakistan-based terrorist groups may carry out attacks in a major city to avenge the hanging of 26/11 terrorist Ajmal Kasab and Parliament attack convict Afzal Guru.
They said the central security agencies had sent an advisory on Tuesday asking all states to tighten security in sensitive places as Lashkar-e-Taiba, Jaish-e-Mohammad and Hizbul Mujahideen may launch attacks.
The security agencies sent another advisory on Wednesday saying banned Indian Mujahideen may carry out terror attacks to avenge the hanging of Kasab and Guru.
Union home minister Sushil Kumar Shinde had on Thursday said all states were alerted about a possible terror strike by militant groups.
However, Andhra Pradesh chief minister Kiran Kumar Reddy had said those were general alerts which often keep coming from the Centre.