The Centre for Public Administration in Emergency Situations's spokesman said late Saturday night the "red-shirts" protesters have held hostage two groups of soldiers.
The Nation online quoted Sansern Kaewkamnerd as saying the army is negotiating with the protesters to secure release of the soldiers.
He declined to give further details, saying the first group comprised eight soldiers while the second group comprised 20 soldiers.
In a nationally-televised TV speech at about 11:25 p.m., Prime Minister Abhisit Vejjajiva said the government and himself will try to further ease the tensions by all means to keep the rule of law and justice.
The confrontation between "red-shirts" and the security forces Saturday evening in Bangkok ceased temporarily as the army retreated.
The PM's Secretary-General Korbsak Sabhavasu was appointed to negotiate with red shirt leaders for a truce, and the army had already withdrawn from the confrontation site, said Sansern earlier Saturday night in a live TV address.
The temporary truce came after hundreds protestors and the security forces conflicted at Khokwua intersection at about 8:10 p. m.
The two sides exchanged fire and the protestors hurled grenades at Khokwua intersection.
So far altogether 11 people were reported dead in the clashes as Nation TV quoted from hospitals. The latest number of injuries is 678 as confirmed by Erawan emergency center by 11:50 p.m. Saturday.