A big explosion rocked late on Tuesday the headquarters of the Central Security in downtown Yemen’s capital Sana’a injuring four troops, informed sources said on Wednesday.

A rocket landed into the middle of the headquarters but those behind the attack were unknown, the sources said, amid reports the attack was in response to a similar attack on the first armored division which deserted from the army and announced peaceful support to the popular uprising seeking the ouster of the regime months ago.

After the explosion, central security forces were placed on high alert and vehicles deployed to streets nearby the compound, the sources said.

The incident comes amid tense clam in Sana’a after heavy clashes between pro and anti-regime forces that triggered fears of civil war in the country.