KIEV - Ukrainians and foreign diplomats marked Friday two years since the murder of top journalist Pavel Sheremet, with supporters accusing authorities of being unwilling to solve the crime.

The award-winning Russian-Ukrainian journalist for Ukrainska Pravda, who was known for his fearless criticism of the Kremlin and Kiev leaders, died when a bomb planted in his car exploded during a morning rush hour in 2016.

His murder sent shockwaves across Ukraine but the case remains unsolved.

On Friday morning, dozens of people laid flowers at the scene of the murder in central Kiev and urged the authorities to explain an apparent lack of firm results in the ongoing probe.

Sheremet's colleagues and friends held black placards reading "Two years. Killers have still not been found".

Ukrainska Pravda editor Sevgil Musayeva-Borovyk slammed the authorities' silence, saying investigators should either announce the results of the probe or acknowledge "their absolute inefficiency."

"Simply staying silent is inadmissible," she said.

She suggested that Kiev authorities did not want to conduct a genuine probe because "the masterminds and killers were somehow linked to representatives of top Ukrainian officials."

Foreign diplomats also paid homage to Sheremet, with US Ambassador to Ukraine Marie Yovanovitch visiting the site of the murder.

"Today, two years since his murder, we remember Pavel Sheremet, a talented and fearless journalist. Those responsible must face justice," the British embassy in Ukraine twitted.

No arrests have so far been made.

Prosecutors said they were pursuing several lines of inquiry and considering various possible motives including Sheremet's professional and private life.

"To date, more than 20 different examinations have been conducted, dozens of people have been interviewed," Andriy Lysenko, spokesman for the Prosecutor General's Office, wrote on Facebook.

The interior ministry said the probe was complicated by the fact that they could not question representatives of the former Moscow-backed authorities, many of whom fled to Russia after a Western-backed popular uprising in Kiev in 2014.

Ministry spokesman Artem Shevchenko said Sheremet had been in contact with "the former authorities" before his death.

A Russian national who was born in ex-Soviet Belarus, Sheremet worked for a top TV channel in Russia.

He quit the country in 2014, the year Russia annexed Crimea after the Kiev uprising and moved to support an insurgency in the east of the ex-Soviet country.

He also founded the popular Belarussky Partizan opposition website after he was detained and expelled from his native Belarus for his criticism of authoritarian President Alexander Lukashenko.