Colombia's leading presidential contender says he is reinforcing security measures after police warned him of a plot to attack his campaign headquarters.

Ivan Duque said Wednesday that police recently briefed him on a purported plot to send a letter bomb to his Bogota offices. He says police would not tell him who was planning the attack but his campaign is taking extra security measures, including the addition of two police motorcycle escorts to his security detail.

The conservative Duque leads polls ahead of Colombia's May 27 presidential election. The election will be the first since a peace deal was reached ending five decades of war with the Revolutionary Armed Forces of Colombia.

Duque has promised to revise some sensitive parts of the peace accord.