ADEN, Yemen, May 14 (Xinhua) -- At least six Yemenis were killed and four others were injured on Tuesday in artillery shelling launched by the Houthis in Yemen's southern province of Dhale, a government official told Xinhua.

The people were killed after two shells fired randomly by the Houthi fighters and targeted their home in Sanah area in the government-controlled province of Dhale, government officials said on condition of anonymity.

The dead included four children and their father and mother, the source said, adding that the injured have been transferred to nearby hospitals for treatment.

Dozens of families started leaving their houses and fleeing the residential areas amid random Houthi shelling and firing, local sources said.

Earlier in the day, UN Special Envoy to Yemen Martin Griffiths tweeted that he is deeply concerned about the ongoing escalation in Dhale, and urged all parties to exercise utmost restraint.

The UN envoy said that any military escalation risks a setback in the progress towards peace in Yemen.

Both warring sides continued to mobilize large numbers of fighters to the frontlines in Dhale amid non-stop armed confrontations taking place since weeks ago in the southern region.

Last month, scores of Houthi fighters launched a series of intense armed attacks on the positions of government forces and succeeded in seizing the district of Al Husha in the west of Dhale.

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

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