A case was registered against an unknown person after a Khalistan flag was found on a bridge on the Amritsar-Delhi national highway in Haryana's Ambala district on Saturday, police said.
Some pro-Khalistan slogans were also found written under the bridge near the Shambhu toll plaza close to Ambala city, they said.
Police said a case has been registered against an unknown person in this regard and further investigation was underway.
Police brought down the flag and wiped off the slogans after getting information.