Ukrainian President Petro Poroshenko called an extraordinary session of the Military Cabinet of the National Security Council on July 13 in an effort to end a confrontation between fighters from a radical nationalist group and police following a deadly shootout in the western city of Mukacheve.

Ukrainian security forces have been seeking the surrender of armed members of Right Sector since the gunbattle on July 11 that killed at least three people.

The standoff with members of Right Sector highlighted tension between the government and nationalist groups that played a role in the protests that pushed Moscow-backed President Viktor Yanukovych from power last year but now challenge the authority of the pro-Western leaders in power.

It highlighted another potential threat to the country's unity amid a conflict with Russian-backed separatists that has killed more than 6,400 people in eastern Ukraine since April 2014 and persists despite a European-brokered cease-fire deal.

Poroshenko's spokesman, Svyatoslav Tseholko, said the Military Cabinet that was created in March includes Prime Minister Arseniy Yatsenyuk and other government members as well as the armed forces chief of staff, the border guards chief, the National Guard commander, and the parliament speaker.

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The Ukrainian Security Service (SBU) demanded on July 12 that armed members of Right Sector surrender to avoid a "bloodbath."

Authorities launched an operation on July 11 to disarm members of Right Sector near Mukacheve, but they apparently hid in the woods near the border with European Union members Hungary and Slovakia.

Officials said two of the men, who were wounded in the shootout, had surrendered and are currently in hospital, while 12 remained defiant.

Conflicting Versions

The cause of the gunbattle was unclear. The sides have different versions of events but Right Sector's response underlines the problems Kyiv has keeping order while trying to carry out reforms and end the Russian-backed separatist rebellion in the eastern regions of Donetsk and Luhansk.

Right Sector presented its battle in Mukacheve as one to root out corruption, saying they had been lured to a sports club on July 11 by a local politician they had accused of smuggling -- a major problem in the western Zakarpattya Province.

The group said they were set upon by local police, who killed two of their members.

The Interior Ministry said Right Sector fighters opened fire first, killing one civilian.

Dozens of supporters of Right Sector protested in Kyiv and other major cities on July 12 to demand the dismissal of Interior Minister Arsen Avakov.

Some officials suggested the violence was a turf war between groups keen to control smuggling routes from Zakarpattya, which borders Hungary, Slovakia, and Romania.

The tense situation in the western region, which is home to a large Hungarian minority and is separated from the rest of Ukraine by the Carpathian Mountains, added to the challenges faced by Poroshenko and his government as it struggles with severe economic problems and the conflict with separatists in the east.

On July 12, Kyiv sent more police to the region to try to persuade the Right Sector fighters to surrender and Poroshenko ordered the police to disarm and arrest those responsible for the shooting.

Right Sector’s leaders said the group would set up checkpoints on roads to stop the flow of police reinforcements, vowing to send their men to Kyiv if Avakov was not sacked.

With reporting by Reuters and UNIAN