ADEN, Yemen, April 8 (Xinhua) -- Fighters of the Houthi group launched an intensified shelling against areas controlled by the Yemeni government in the southern province of al-Dhalea on Monday night, causing several explosions, a security official told Xinhua.

The security source based in the province said on condition of anonymity that "Katyusha rockets fired by the Houthi rebels landed in the government-controlled district of Qa'atabah District and in the nearby area of Snah."

A number of local residents confirmed hearing various huge explosions in different parts of the government-controlled province of al-Dhalea.

For the first time in years of the ongoing military conflict, the Houthi-fired missiles have managed to target these areas controlled by the government, according to the local residents.

An official of the local government authority in al-Dhalea told Xinhua that the Iranian-backed Houthis fired two ballistic missiles that landed in non-residential areas in the province, causing no casualties.

On Saturday, ferocious battles took place in the country's southern province of al-Dhalea and resulted in the killing of some 80 fighters belonging to the Iranian-allied Houthi group, including key leaders, said the pro-government Giants Brigades in a statement.

Last week, the Houthis launched a series of intensive attacks on positions of the government forces in the northern part of al-Dhalea and managed to control key mountainous hills overlooking government-controlled areas in the province.

The areas in the north and west of al-Dhalea have been witnessing continuous fighting between government forces and Houthi fighters for nearly four years.

Yemen has been plagued by a civil war since late 2014 after Houthi rebels revolted against the internationally recognized government of President Abd-Rabbu Mansour Hadi.

The rebels advanced from their far northern stronghold of Saada Province toward the south, and seized control over much of the country's north including Sanaa, thus triggering the civil war.