YEREVAN -- Demonstrators and Armenian riot police clashed after lawmakers nominated Serzh Sarkisian to be the country’s next prime minister amid a wave of protests accusing the longtime former president of a power grab.

Protest leader Nikol Pashinian was taken to hospital on April 16 with cuts and an eye injury after police moved in to stop the opposition lawmaker and others from entering parliament.

Pashinian’s wife told RFE/RL that the protest leader was taken to the Nairi Medical Center in Yerevan to be treated but that he intended to return to join thousands of Armenians who have been protesting Sarkisian’s expected approval as prime minister.

Demonstrators have been rallying since April 13, blocking streets in central Yerevan to protest plans for Sarkisian to shift to the prime minister's post just days after he left the presidency following a decade in office.

The ruling Republican Party of Armenia and the Armenian Revolutionary Federation (Dashnaktsutyun) factions on April 16 unanimously approved Sarkisian as the nominee for the post. Parliament is expected to vote on the matter on April 17.

The protesters, many waving Armenian flags, clogged Marshal Bagramian Avenue, which leads to the National Assembly building, stopping traffic in the process. Lines of riot police stopped the crowd from advancing further toward parliament.

They later rolled out razor wire to hold the surging crowd back, with some local media reporting the use of tear gas and stun grenades as well. Three police were also injured in the clashes, the reports said.

"Something unprecedented is happening in Armenia: the same person wants to become the country's leader for a third time. We cannot let this happen," Pashinian, the outspoken head of the opposition group Civil Contract, said.

"The time has come to liberate Armenia's citizens. With this minor inconvenience we are trying to save you from a greater inconvenience called Serzh Sarkisian," Pashinian shouted repeatedly through a megaphone to the crowd.

WATCH: Live coverage of the Yerevan protests

In a statement issued early on April 16, police said the protests were illegal and warned that law enforcement had the authority to forcibly "discontinue" street gatherings accompanied by "collective breaches of public order."

"The constitutional right of free movement of thousands of citizens is being restricted,” a police statement said. “The police can stop the assembly if they evaluate that it is not possible to prevent the disproportionate restriction of the rights of others or the interests of the public."

Sarkisian was first elected in 2008 in the South Caucasus country of about 3 million people and served two terms, stepping down when the new president, Armen Sarkisian -- no relation -- was inaugurated on April 9.

Under a shift that was approved in a December 2015 referendum and is now in place, Armenia changed its form of government and handed more powers to the prime minister, downgrading the president -- now also elected by parliament -- to more of a figurehead position.

Serzh Sarkisian had promised in 2014 that he would "not aspire" to the post of prime minister if Armenia switched from a presidential to a parliamentary system as a result of the referendum. Pashinian and other opposition leaders now accuse him of breaking that pledge.

Sarkisian has also faced criticism from opponents who accuse the government of Armenia, which gained independence in the 1991 breakup of the Soviet Union but relies on Russia for aid and investment, of corruption and economic mismanagement.

Two opposition lawmakers set off smoke flares in parliament last week to protest Sarkisian's election as prime minister.

Many members of the ruling party contend that the 64-year-old Sarkisian is the best candidate for prime minister given his lengthy experience, especially when it comes to talks over neighboring Azerbaijan's breakaway Nagorno-Karabakh region.

Clashes over control of Nagorno-Karabakh, which is in Azerbaijan but is controlled by ethnic Armenians, have intensified in the past three years and there was a flare-up in violence there in April 2016.

"If my candidacy is approved...I am going to spend a great deal of time sharing experiences that I have accumulated in different positions over the years," Sarkisian said in an interview with the Russian media outlet Izvestia published on April 16.

With reporting by Sisak Gabrielian, Karlen Aslanian and Narine Ghalechian