Arsenal's Olivier Giroud looks dejected after being sent off during a Champions League Group F match against Dinamo Zagreb at the Maksimir Stadium in Zagreb, Croatia, Sept 16, 2015. [Photo/Agencies]

ZAGREB - Dinamo Zagreb made a dream start to their Champions League campaign after a goal in each half gave them a 2-1 home win over 10-man Arsenal in their Group F match on Wednesday.

An Alex Oxlade-Chamberlain own goal followed by a Junior Fernandes header put Dinamo in the driving seat before Theo Walcott pulled one back for the Premier League side, who had striker Olivier Giroud sent off in the first half.

Having failed to advance past the group stage of Europe's elite club competition in their previous four attempts, Dinamo produced a morale-boosting performance in the Maksimir stadium.

Arsenal manager Arsene Wenger blamed the defeat on bad luck although he might also question his side's poor defending at set-pieces and a lack of creativity in midfield.

"It is not the way we wanted to begin the competition but I think we were a bit unlucky as well today," Wenger told BT Sport.

"At 2-0 down...we gave it our all against a team that defends in their own half but unfortunately we couldn't get back."

Organised defending aided by a packed midfield frustrated a disjointed Arsenal and the home side always looked dangerous on the break, with Algeria striker El Hilal Arabi Soudani at the heart of all their moves.

Arsenal held the upper hand in the opening 20 minutes as Giroud missed two good chances, hitting the post with a scuffed effort after Dinamo's Portuguese keeper Eduardo had kept out the Frenchman's header with an acrobatic save.

The Croatian champions took the lead against the run of play with Chamberlain unable to get out of the way of a rebound after Arsenal keeper David Ospina blocked a close-range shot by left back Josip Pivaric.

Worse followed for the visitors when Giroud was shown a second yellow card for a reckless challenge after he was earlier booked for dissent.