Belgian special forces police stormed an apartment in the western city of Ghent on Monday to end a siege after reports that gunmen had taken a hostage there.

The victim was safe and well and three other men had been detained, a spokeswoman for state prosecutors said.

Special forces police were called to a neighbourhood in Ghent in western Belgium after reports that four armed men had entered an apartment building. (Geert Vanden Wijngaert/Associated Press)

"Three men have been taken away though there were no weapons found. The earlier reports were of four men with kalashnikovs," she said. "It's not entirely clear whether someone was in fact taken hostage."

Armed police in balaclavas emerged at about 1 p.m local time from the cordoned-off building in the Dampoort district.

"It's over," one police officer said.

Belgian broadcaster VRT cited neighbours as saying that the apartment had been used by drug dealers.

The incident occurred within hours of Australian police locking down the centre of Sydney after an armed man walked into a downtown cafe, took hostages and forced them to display an Islamic flag.

The Belgian prosecution spokeswoman said there was no indication of a link in the Ghent case to an extremist group.

"It's really nothing along the lines of what is happening in Sydney," she said.