A gunman threw grenades and opened fire on worshippers at a mosque, in Yemen's southern capital, Sanaa, late on Tuesday, killing four people and wounding 15 others, a security official said.

"The Shiite gunman hurled two grenade bombs and opened fire on the worshippers in Bani Bahlol mosque, during evening prayers, killing four and injuring 15 others," the official said, on condition of anonymity.

The gunman fled, said the official, adding that, the incident was apparently for "political and sectarian revenge from Sunni branch of Islam."

Sanaa, the capital of Yemen, which has been under control of Shiite Houthi group, since it overthrew the government in Sept, 2014, is awash of gunmen, weapons and lawless acts, after the judiciary system and security apparatus have been suspended.

Security in Yemen has deteriorated since Mar, 2015, when war broke out between the Shiite Houthi group, supported by former President, Ali Abdullash Saleh, and the government, backed by a Saudi-led Arab military coalition.

The current security vacuum was exploited by terrorist groups, which also took advantage of the ongoing civil war to expand its influence and control more territories in lawless parts of the country.

Last week, a grenade exploded outside a mosque in Sanaa, controlled by the Iran-allied Houthi group, as worshippers were leaving after midday prayers. There were no casualties.

The Daesh branch in Yemen claimed responsibility, last Sept, for a bomb attack on a Shiite-controlled mosque in Sanaa, that killed 10 worshippers.