The slogans were seen at Karol Bagh and Jhandewalan Metro Stations.  

Reportedly, the slogans were written by supporters of Sikhs For Justice, a banned Sikh separatist group based in the United States.  

An FIR has been filed by the Delhi police, and CCTV footage of the two metro stations has been obtained from the Delhi Metro authorities.  

A security guard at a building close to the Karol Bagh Metro station said that he noticed the writing in black paint on the pillars of the metro station when he came for duty on Sunday morning.  

"I came to duty at 8 am and saw that something was written in black colour on the pillars of the metro station. A huge crowd had gathered there and was reading the slogans," Bajrangi, the security guard, said. 

"These slogans may have been written at night because no one was there at that time and no one saw who wrote these slogans," he added.  

In a similar incident in January this year, the Delhi police apprehended a man for his alleged involvement in making pro-Khalistani graffiti on walls in Delhi's Tilak Nagar area.  

In August last year, the Delhi police Special Cell detained two persons from Punjab in connection with pro-Khalistan graffiti and slogans painted at more than five metro stations in Delhi. -- ANI