Followers of the Houthi group demonstrate against the Saudi-led air strikes on Yemen, in Sanaa April 1, 2015.[Photo/Agencies]

ADEN -- Dozens of well-trained foreign troops arrived Thursday in Yemen's southern port city of Aden, where fierce street fighting is taking place between gunmen of the Shiite Houthi group and tribal militia allied with Yemen's President Abd-Rabbu Mansour Hadi.

"Scores of well-trained troops from various nationalities have just landed at the port apparently to confront the pro-Houthi forces on the ground," an official at Aden port told Xinhua on condition of anonymity.

The official did not elaborate on the nationalities of the foreign troops, but said they may participate in the fighting with Hadi's forces against the Houthis to regain full control over Aden.

At the same time, hundreds of Houthi gunmen, backed by security forces, engaged in fierce fighting with tribal militia in Aden's district of Cirater.

Local residents told Xinhua that "a number of houses were bombarded by tanks shells, causing casualties among civilians."