Georgia's prime minister resigned Thursday over plans to arrest a top opposition leader, deepening a political crisis that has gripped the Caucasus nation since elections last year.

Giorgi Gakharia, a 45-year-old with the ruling Georgian Dream party who was prime minister since 2019, said he was stepping down because of disagreement in the government over enforcing a court order to arrest Nika Melia.

The move to detain Melia -- the chairman of the United National Movement of ex-president Mikheil Saakashvili -- sparked outrage in the opposition and warnings from Georgia's Western allies.

With opposition party leaders gathered at the UNM headquarters in Georgia's capital Tbilisi and television reports showing riot police mobilising nearby, Gakharia said he could not enforce the court order and would resign.

"It is inadmissible to enforce a judiciary decision... if that poses a risk to the health and lives of our citizens or creates the possibility of a political escalation in the country," he said.

A court in Tbilisi on Wednesday ordered Melia placed in pre-trial detention after he refused to pay an increased bail fee ahead of hearings in a case related to anti-government demonstrations in 2019. He has been charged with "organising mass violence" during the protests and is facing up to nine years in prison.

Call for snap elections

Melia, 41, rejects the case as politically motivated and his supporters have vowed to obstruct police if they move to arrest him.

The detention order has raised the stakes in the crisis over October's parliamentary elections, which the opposition denounced as rigged after Georgian Dream claimed victory.

Opposition members have refused to take up their seats in the new parliament and demanded new elections.

Melia told journalists Thursday that the opposition was ready for talks on a snap vote. "Power will change in Georgia peacefully and very soon," he said.

The interior ministry said it had "temporarily postponed the planned detention" of Melia in connection with the prime minister's resignation.

The ruling party's chairman, Irakli Kobakhidze, said its leadership would decide by Friday on a candidate to take over as prime minister, adding that he "regretted" Gakharia's decision. "I urge Melia to obey the court decision. Otherwise, the government will enforce the judiciary decision and arrest him," he told a news conference.

Melia is accused of fomenting violence during protests that erupted in Tbilisi in June 2019 after a Russian lawmaker addressed parliament from the speaker's seat, a controversial move in a country where ties with Moscow remain strained after a brief war in 2008.

The rallies saw thousands of protesters clash with police who used tear gas and rubber bullets against the crowds.

'Dangerous situation'

Then-interior minister Gakharia led the crackdown and was appointed premier in September 2019. Dubbed "Moscow's man" by the opposition, Gakharia worked in Russia as a regional director for German aviation company Lufthansa and is a graduate of Moscow's Lomonosov University.

Georgia gained its independence with the 1992 collapse of the Soviet Union and in the decades since has been divided between its longstanding relationship with Moscow and efforts to seek closer ties with the West.

In a statement ahead of Melia's trial, the European Union envoy to Georgia, Carl Hartzell, described the circumstances surrounding his prosecution as a "dangerous trajectory for Georgia and for Georgian democracy".

The US embassy in Tbilisi said on Twitter that the crisis "must be resolved peacefully", urging restraint on all sides. "The current dangerous situation following the Melia ruling stems from decades-long problems with the electoral system and the judicial system," it said.

In power since 2012, Georgian Dream has seen its popularity fall over its failure to address economic stagnation and perceived backsliding on commitments to democracy. Critics accuse Georgia's richest man Bidzina Ivanishvili -- the founder of Georgian Dream who is widely seen to be calling the shots in the country -- of persecuting opponents and fostering corruption.