Spanish police arrested Vladimir Milisavljevic, one of the fugitive convicts in the 2003 assassination of Serbian prime minister Zoran Djindjic, they said on Friday.

Milisavljevic, on the run after being convicted in 2007 along with 11 others for the killing, was arrested Thursday in a restaurant in the eastern city of Valencia, along with Serbian gang leader Luka Bojovic, a police statement said.

Bojovic is the leader of the "Zemun Clan", a mafia gang that developed from the "Tigers of Arkan" paramilitary group, "known for its cruelty during Balkan wars" of the 1990s, the statement said.

Milisavljevic was described as a lieutenant of Bojovic, who rose to head the Zemun Clan after the convictions for Djindjic's killing.

Bojovic was not among those convicted of the assassination but was wanted by Serbian police and Interpol for more than 20 other killings in Serbia, Spain and the Netherlands.

He was also wanted for trafficking of people, drugs and arms and prostitution offences, the statement said.

Milisavljevic was sentenced in absentia to 35 years' jail for his role in the killing of Djindjic, gunned down in Belgrade in 2003. He was among five convicts who stayed on the run following the sentencing in 2007.

Police said he had travelled from Spain's Canary Islands via Madrid to Valencia to meet up with Bojovic and other gang members.

Police said they also arrested a hitman for the gang, Sinisa Petric.