The Home Ministry has directed the Delhi Police to tighten security in and around the national capital ahead of the Commonwealth Games.The directive came following a review of Delhi's security after the firing incident near Jama Masjid in which two Taiwan nationals were injured. Home Secretary Gopal K Pillai today took stock of the Commonwealth Games security and crowd controlling measures. Official sources said that the meeting also discussed effectiveness of CCTVs and other security mechanism being installed in the Games village and venues.A four-tier security apparatus is being put in place during the Games.