Turkish Foreign Minister Ahmet Davutoglu has contacted U.S. Secretary of State John Kerry to object to recent statements from Washington expressing concern over Turkey's handling of mass anti-government protests, a foreign ministry diplomat told Agence France Presse Wednesday.

"Turkey is not a second-class democracy," Davutoglu told Kerry in a phone call late on Tuesday, the diplomat said on condition of anonymity.

A group representing Turkey's protesters on Wednesday urged the government to fire the police chiefs of Istanbul and Ankara and other cities where security forces have violently cracked down on political protests as Turkish police fired tear gas and water cannon to disperse crowds who joined the mass demonstrations.

"We demand that those police chiefs... who are responsible for violence and pressure are dismissed," a spokesman for the protesters told reporters as he read a list of demands after meeting with Deputy Prime Minister Bulent Arinc in Ankara.

Fresh violence erupted early Wednesday as protesters defied a government plea to end days of deadly unrest, the biggest challenge yet to Prime Minister Recep Tayyip Erdogan's decade-long rule.

Police used tear gas and water cannon on hundreds of protesters, who ignored warnings to disperse in Istanbul, Ankara and the southeastern city of Hatay, where a young protester died a day earlier.

The White House praised Turkey's government Tuesday for apologizing for the use of force against protesters in the biggest mass demonstrations of Prime Minister Recep Tayyip Erdogan's decade in power.

Deputy Turkish Prime Minister Bulent Arinc said earlier the government had "learnt its lesson" and regretted using security forces against people with "rightful demands."

Turkish Prime Minister Recep Tayyip Erdogan, facing unprecedented popular protests at home, charged on Tuesday that Syrian President Bashar Assad has committed atrocities worse than those attributed to his notorious father.

"Assad has surpassed his father in crimes and massacres, and it is not possible to forgive that. He will have to pay the price sooner or later," Erdogan said during a speech in Algeria, which he is visiting on a four-day tour of North Africa.

The Turkish army returned fire after shots were fired at military targets from across the border with Syria, the military said in a statement Tuesday.

"A group on the Syrian side of the border fired 60 shots at an armored personnel carrier and tactical vehicles... which was reciprocated in kind" late on Monday, it said, adding that there was no damage or casualties.

Turkish premier Recep Tayyip Erdogan left Morocco for Algeria on Tuesday, the second leg of a North African tour, as the worst political crisis of his 10 years in power showed no sign of abating.

After arriving on Monday at the head of a senior ministerial delegation and accompanied by a large number of businessmen, he and Moroccan counterpart Abdelilah Benkirane signed a joint political declaration on developing strategic ties, official Moroccan media said.

Turkey's government apologized on Tuesday to protesters hurt in clashes with police during days of demonstrations and called for an immediate end to the protests.

Deputy Prime Minister Bulent Arinc moved to calm tensions after days of street clashes that have left at least two people dead, saying the government had "learnt its lesson" from the disturbances.

A 22-year-old man died in a hospital after being shot during anti-government protests in southern Turkey, the NTV television reported Tuesday.

"Abdullah Comert was seriously wounded... after gunfire from an unidentified person," the station reported, quoting a statement from the local governor's office in the Hatay province.

U.S. Secretary of State John Kerry on Monday voiced concern over "reports of excessive use of force" by Turkish police in clashes with demonstrators in Ankara and other Turkish cities.

Kerry stressed that the United States supported the right to peaceful protests and said Washington was "deeply concerned about the numbers of people injured," urging all sides to "avoid any provocations or violence."