|Indian police and security forces have been on high alert ever since the attacks in 2008 [AFP]
Police in the Indian city of Mumbai said they are on the search for four men suspected of entering the city to carry out an attack.
Himanshu Roy, a police official said on Friday that they have "credible information that at least four men belonging to the Pakistan-based group blamed for the 2008 Mumbai attacks have entered the city".
The official added that the suspects are believed to be plotting "violent attacks that are going to cause
A three-day siege of the Indian financial capital in November 2008 left 166 people dead.
On Thursday, police said four men - Walid Jinnah, Abdul Karim Musa, Noor Abdul Elahi and Mehfooz Alam - sneaked into Mumbai to carry out attacks.
At a news conference, the police released a sketch of Jinnah, calling him the leader of the group.
The warning follows a bomb blast earlier this month at a Hindu temple in the city of Varanasi, which killed one and injured several others.
In February, another bomb blast at a bakery in the western city of Pune killed over 15 people and injured scores. Investigations in both those blasts are still under way.
A member of the group which carried out the 2008 Mumbai attacks has been sentenced to death.
Pakistan has charged seven people for involvement in the attacks, but has not yet sentenced anyone.