BANGKOK, Jan. 27 -- Thai army chief Prayuth Chan-ocha on Monday pledged to closely work with the government-run Center for Managing Peace and Order (CMPO) to further strengthen security following the death of a core protest leader on Sunday.

Army spokesman Winthai Suwari said Monday morning that the army expressed concerns over the clash between protesters and pro- government supporters during advance votings on Sunday, which led to the death of Suthin Tharathin, a core protest leader, and the injury of 13 others.

Winthai said the army would ask the CMPO to tighten security at violence hotspots.

Suthin, leader of the People's Army to Overthrow the Thaksin Regime, was shot in the head outside the polling station in Wat Sri-iam Temple compound in the capital on Sunday.

According to the Bangkok Metropolitan Administration's Erawan Emergency Medical Service Center, clashes between pro-government supporters and protesters since Nov. 30, 2013 have left at least ten people killed and 571 others injured.