UPDATE 1-Soccer-Police arrest rioting fans before Croatia derby

(Updates after match)

ZAGREB, April 4 (Reuters) - Police arrested 40 rioting Dinamo Zagreb fans on Wednesday before the champions beat arch-rivals Hajduk Split 3-2 on aggregate to reach the Croatian cup final.

Dinamo will now play Slaven Belupo Koprivnica, who reached their first final with a 3-2 home win over holders Rijeka after a goalless first leg.

"The police have arrested 40 Bad Blue Boys for destroying cars and motorcycles in Split," local police spokeswoman Marina Kraljevic Gudelj told state news agency Hina.

She said the fans had probably arrived on a night train from Zagreb and almost immediately went on the rampage. Police confiscated 24 baseball bats and a number of flares.

Dinamo and Hajduk, who have won 14 league titles between them since independence in 1991, have a bitter rivalry which intensified after Croatia's secession from Yugoslavia.

They drew 2-2 on Wednesday, with Dinamo fighting back from 2-0 down to go through.

Dario Damjanovic headed in Hajduk's first goal from Igor Musa's corner in the 39th minute and Bosnia midfielder Mladen Bartolovic gave them a 2-1 aggregate lead with a long-range effort on the stroke of halftime.

The visitors piled on the pressure after the break and Brazilian substitute Sammir was instrumental in swinging the tie their way after coming on for Mihael Mikic on the hour.

After several incisive runs, his defence-splitting pass left Luka Modric with a simple finish that gave Dinamo the vital away goal in the 76th minute and Josip Tadic completed the comeback with a fine solo run a minute before time.

A Bojan Vrucina header, a Matija Kristic volley and Miljenko Mumlek's penalty on the hour gave Slaven a 3-0 lead against Rijeka before the visitors set up a dramatic finish through Ahmad Sharbini and Bulgarian Aleksandar Ivanov.