Hundreds of disgruntled Ukrainian activists gathered on Wednesday in a tent camp outside parliament to demand a more forceful fight against government graft.

Some had spent the night there following a rally on Tuesday that drew nearly 5,000 people and saw calls for President Petro Poroshenko to resign.

The protesters have set up several dozen khaki-green tents in a park and street that run alongside the parliament building -- and they appeared intent on staying put until their demands were met.

An AFP team saw activists sip tea and chat outside parliament while hundreds of riot police officers with batons watched.

But national police chief Sergiy Knyazev and Prosecutor General Yuriy Lutsenko said they had no intention of touching the tents.

Lutsenko called the right to protest "one of the main achievements" of the February 2014 pro-EU revolution that toppled Kiev's Kremlin-backed regime and pulled Ukraine out of Russia's orbit.

Large tent camps featured prominently during that revolt as well as one in 2004 that forced the authorities to annul the results of a disputed election claimed by the Kremlin-backed candidate.

Their return underscored a growing sense that the promises made during the 2014 uprising have gone unfulfilled by Poroshenko and his Western-backed team.

"Elements from Ukraine's 'old' system are defending their interests and seeking retribution against anti-corruption actors," the London-based Chatham House international affairs institute said in a report on Wednesday.

Prime Minister Volodymyr Groysman meanwhile reaffirmed his commitment to the fight against corruption.

But Groysman also accused some of those leading the rallies of having a "thirst for power and -- what is worst of all -- trying to use their slogans to destabilise the situation in the country".

- Anti-corruption court -

The protesters have three main demands.

They include stripping lawmakers of immunity from prosecution and launching an anti-corruption court that Kiev's lenders at the International Monetary Fund have said would be a "benchmark" of Ukraine's progress toward Western standards.

They also want changes to the electoral system that would help independent lawmakers gain seats.

Poroshenko appeared to respond to the mounting political pressure by introducing a bill on Tuesday that would eliminate lawmakers' immunity starting in 2020.

Protest organisers dismissed it as a token gesture that needlessly delayed the long-promised change.

Ukrainian parliament speaker Andriy Parubiy said lawmakers would debate the immunity and election law issues on Thursday.

But National Security and Defence Council secretary Oleksandr Turchynov seemed to confirm the current volatility of politics in Ukraine by cancelling a scheduled meeting in Brussels on Wednesday with NATO chief Jens Stoltenberg.

Turchynov's office told the Interfax news agency that the visit was called off "due to the domestic situation and the escalation of the situation in the east".

Kiev said four soldiers had been killed since Tuesday in an apparent uptick in fighting against Russsian-backed insurgents in a war that has claimed more than 10,000 lives.

Source: AFP