Yemen's president has warned of sectarian violence in his country after deadly clashes continued for a second week in the restive north between rebels from a branch of Shia Islam and ultraconservative Sunnis.

In remarks aired on Tuesday by state TV, President Abed Rabbo Mansour Hadi denounced "sectarian fighting that does not serve the security or stability of the nation".

Rebels known as Houthis are clashing with conservative Salafis and jihadists in the city of Damaj, in the northern Saada province.

Hadi called for both sides to practice "self-restraint".

A UN envoy to Yemen, Jamal Benomar, was in contact with both camps to end the fighting.

Since Wednesday, at least a hundred people have reportedly died in fighting between the two groups.

Members of the Houthi community, who say they have been marginalised politically and economically, have been battling the central government for nearly a decade.

This fighting, however, has amplified the sectarian dimension of the conflict in  remote northern Saada province, which has long been virtually inaccessible to reporters.

Al-Qaeda attacks

Violence also continued in the country's south, where Al-Qaeda in the Arabian Peninsula (AQAP) launched a series of attacks against the government.

The armed group said it was retaliating against US drone attacks which have targeted its fighters.

On Tuesday, a Yemeni official said that authorities arrested four suspected al-Qaeda fighters in connection with a spate of assassinations of police and army officers in the restive southeast.

The arrests were made in the Hadramawt province town of Ghayl Bawazir on Monday and Tuesday, the official said.

AQAP has intensified its attacks on the Yemeni security forces, taking advantage of the weakening of central government authority since a popular uprising toppled veteran president Ali Abdullah Saleh in 2011.

“Despite the ongoing government military operation and US drone attacks, al-Qaeda is far from defeated in Yemen," Al Jazeera's Hashem AhelBarra, reporting from Sanaa, said.

"The group remains very active in the south of the country where it enjoys tribal protection. And it is even expanding in some areas where there is no significant military presence," he added.

Source: Al Jazeera and agencies