Police gather outside a restaurant near the scene of an attack in central Jakarta January 14, 2016.[Photo/Agencies]

The Jakarta Police has declared first-level security alert in the capital following a series of blasts in downtown area on Thursday.

While most of the police force have been deployed to the blast scene and surrounding area, the police have also increased security measures around its headquarters.

"Today, we declared first alert. There are more than one guns [put on standby] at each gate now. Normally we only have one," said Adj. Comr. HS. Hasibuan, the police security head at the headquarters in south Jakarta on Thursday.

The three entrances at the headquarters were seen closely guarded by armed officers. Everyone passing any of the gates was subjected to the officers’ clearing before they could come into the headquarters complex.

"Please open your bag. Where are you going?" an officer told a visitor at the headquarters’ main entrance.

Previously, the perpetrators reportedly escaped the police hunt around Semanggi where the headquarters is located. The police patrol siren often heard at the highway in front of the headquarters led by Jakarta Police Chief Insp. Gen. Tito Karnavian, previously head a police counter-terror unit Densus 88 from 2009-2010.

The police have also closed a road that links the headquarters and Jl. MH Thamrin, where the blasts occurred.

Hasibuan said that they had not learned about the attack before.

"Actually, we just ended our first alert several days ago after the Christmas and the New Year’s Eve," he said.