The city crime branch has detained two persons in connection with telephone calls to the police control room, threatening to kill Gujarat Chief Minister Narendra Modi.

The security of Modi, who enjoys Z-plus protection, has been beefed up following the calls made late Sunday night, police said on Tuesday.

While confirming the detention of two persons, sources said the duo was being interrogated, but declined to reveal their identity due to the sensitive nature of the matter.

According to police control room, an anonymous caller said two persons were in the city to assassinate Modi and an IPS officer, whose name was withheld, at a public function, while the second caller gave specific locations where the hit men would kill the CM.

"The caller, identifying himself as Ajay, gave the names of the persons who would do the job and even the specific location where the plot was to be executed," the officer, who did not want to be named said, adding the call was traced to a location in Juhapura area of the city.