SANAA: An international human rights group urged Yemen's government Saturday to crack down on human rights violations it says have taken place since the country's 2011 uprising.

Human Rights Watch, in a statement, also urged Yemeni authorities to investigate the death of at least four protesters who died in clashes with security forces in the city of Aden on Thursday.

The group said President Abed Rabbo Mansour Hadi had failed to fulfill a pledge to form a committee to investigate human rights crimes committed during the uprising.

"President Hadi should crack down on rights abusers and consolidate the rule of law," said Joe Stork, HRW deputy Middle East director.

The group noticed some improvements in Yemen but also expressed concern over the slow pace of reform.

Meanwhile, clashes between protesters and security forces broke out Saturday in the southern province of Hadramawt, where insurgents are fighting for secession from the country. One protester from a separatist movement was killed and three others wounded, activist Nasser Baqazqouz said.

Baqazqouz said protesters set fire to two headquarters of the Islamist Islah party in Hadramawt, accusing the Islamists of taking part in demonstrations Thursday where they voiced their strong opposition to southern secession.

In a separate attack the coastal city of Aden, Colonel Abdel-Hafez al-Saqqaf, an army commander, told The Associated Press that one soldier was killed and three others wounded Saturday by unknown men firing machine guns.

Al-Saqqaf doubted that southern secessionists were behind the shooting. Instead he accused members of Al-Qaeda of slipping into the ranks of the demonstrators, who have been protesting against the central government since last week, with the aim to kill security forces.

Security forces were deployed heavily in Aden Saturday as protesters continued to block several main streets and burn tires. Many shops have closed in response to a call for civil disobedience by the secessionist Southern Movement. Traffic in most main streets has been very slow or stand-still.

Mohammed Huzam, a shop-owner in al-Mualla neighborhood in Aden, said he feared demonstrations would turn violent so he closed down his shop. Others however have voluntarily taken part in the civil disobedience.

An activist with the Southern Movement in Aden, Adnan al-Ajam said a stray bullet wounded a man Saturday in the Shiekh Othman neighborhood. He said many people have stayed indoors for fear of shooting.

Al-Ajam said the government was responsible for the deaths, saying that "security forces have been using excessive force as a means to defy the sentiments of the people and their right to demonstrate peacefully."

Flags of the formerly independent South Yemen have been flown from many buildings in Aden. Yemen's north and south were merged in 1990 but later southerners complained of being discriminated against by the northerners.

Separately, a militant website close to Al-Qaeda said that one of two men killed yesterday by government troops in Aden was a well-known journalist and Al-Qaeda member named Wajdi al-Shaabi. The website also published photos of him with the group's leader in Abyen province, an Al-Qaeda stronghold.