People hold signs with a picture of Macedonian Prime Minister Nikola Gruevski during an anti-government protest in downtown Skopje on May 17, 2015
Skopje (AFP) - Macedonia's opposition vowed to continue street protests after 20,000 people marched through the capital Skopje on Sunday demanding that the country's embattled Prime Minister Nikola Gruevski step down.
With the small Balkan country divided by a deep political crisis -- and still in shock after last weekend's battle with ethnic Albanian gunmen in which 18 died -- Gruevski's supporters are to march on Monday after Sunday's big show of force by the opposition.
"We will stay here in front of the government. Nikola Gruevski must resign," the leader of the main opposition SDSM party Zoran Zaev told the crowds drawn up in front of the government's neo-classical offices. "Until he goes we are not going to leave either."
Gruevski -- who only months ago seemed to have an unshakable grip on power -- is now under pressure to assemble as many supporters for his rally in the capital on Monday evening.
Waving Macedonian and Albanian flags, opposition protesters chanted "Resignation!" and "Victory! Victory!" The rival demonstrations come after a year-long stand-off between Gruevski and his centre-left opponents that has split the multi-ethnic country of two million people.
"Join us, for you, for your children, for free and prosperous Macedonia," Zaev urged the protesters, calling the ongoing political crisis "one of the most severe since Macedonia's independence."
"It is necessary to reach a political agreement for an interim government... that would create conditions for early free and fair parliamentary elections," Zaev said.
An opposition source told AFP that they plan to keep enough protesters in front of the prime minister's offices "to keep the pressure on the government."
But by Sunday evening only around 100 remained in tents around a small stage set up opposite the grandiose white edifice, one of several monumental landmarks built by Gruevski during his nine years in power.
"We are going to stay to the end, we are going to bring down the head of this government," said Lazar Popovski, 51, a shopkeeper from Kumanovo, the northern town that was the scene of last weekend's violence.
- 'As long as it takes' -
The bloody shootout between police and ethnic Albanian rebels, many of them from just across the border in Kosovo, was the worst in the former Yugoslav republic since a short 2001 conflict between the government and ethnic Albanians fighters, and raised fears of heightening ethnic tensions.
Albanians make up about one quarter of Macedonia's population.
However, Sunday's protest brought together demonstrators from all ethnicities of the tiny landlocked country, with protesters also carrying flags from the Turkish and Roma minorities.
Another protester from Kumanovo, 33-year-old psychologist Aleksandar Krstevski told AFP: "We will stay as long as it takes, until the final victory, until the prime minister's resignation."
Carrying a placard saying "Goodbye Nikola", 29-year old Jelena said, "There is a need to finish with this government."
Thirty alleged gunmen held after the Kumanovo shootout, including 18 ethnic Albanians from neighbouring Kosovo, have been charged with terror offences.
But the opposition and analysts have suggested the timing of the violence was suspicious, given the huge pressure on Gruevski's government.
Zaev's opposition Social Democratic Union of Macedonia (SDSM) is calling for the government to resign, accusing the ruling party of wiretapping up to 20,000 people, including politicians, journalists and religious leaders.
Zaev has released snippets of the alleged recordings that appear to show widespread government corruption, a murder cover-up and other wrongdoings.
His party has also boycotted parliament since an election in April last year, accusing Gruevski's VMRO-DPMNE party of voting fraud.
"The time has come to show that we no longer want to live in a state led by Gruevski," the SDSM said in a statement.
Gruevski has remained defiant, insisting in an interview Saturday that he would not resign.
He claims the opposition protests have been stirred up by foreign secret service agencies.
His government denies making the phone recordings released by Zaev. It has conceded, however, that the voices are authentic, although it says some are heavily edited or taken out of context.
The government in turn accuses Zaev and his followers of spying and of trying to destabilise the country.
- 'Survival manoeuvre' -
Gruevski, Zaev and ethnic Albanian party leaders held talks this week to resolve the crisis, which could further hamper Macedonia's stalled bid for EU and NATO membership.
All sides pledged to condemn violence and support democratic values, but there was little sign of a solution.
Two ministers and the intelligence chief resigned on Tuesday, after being accused of involvement in the wire-tapping scandal.
But Muamer Pajaziti, an ethnic Albanian Macedonian professor on European integration at Pristina University, said the resignations were only "a survival manoeuvre" by an increasingly unpopular government.
"The opposition and the public will not accept it as a solution. There is a critical mass for change led by the opposition. Slowly, on a larger scale, there are preparations for a broad anti-government coalition," Pajaziti told AFP.