Arsenal's Premier League title hopes suffered a huge blow with a shock home defeat as Watford secured their first top-flight win over the Gunners since 1988.

Former Tottenham defender Younes Kaboul lashed in the opener within 10 minutes for Watford with a shot from outside the area which deflected off Aaron Ramsey.

Just two minutes and 57 seconds later, the visitors doubled their lead as Troy Deeney tapped in the rebound after Etienne Capoue's fine run ended with his shot being saved by Petr Cech.

The Arsenal goalkeeper was called into action again as he tipped Sebastian Prodl's header over the crossbar and pushed away Daryl Janmaat's curling strike.

The hosts improved significantly in the second half and Alex Iwobi pulled a goal back by steering Alexis Sanchez's cross home.

Lucas Perez struck the crossbar with a powerful drive, but they could not find the equaliser.

Going into this game they were unbeaten in their last five league fixtures, but a desperately poor first half showing - with manager Arsene Wenger watching powerless from the stands as he served the second of a four-match touchline ban - cost them dearly.

The Gunners failed to get a shot on target in the first 45 minutes, but forced Watford goalkeeper Heurelho Gomes into sharp saves from substitute Theo Walcott and Iwobi after the break, while the Brazilian pushed away Mesut Ozil's snap shot.

But they suffered their first defeat at the Emirates Stadium since the opening day against Liverpool, ending a run of eight victories and two draws.

Watford boss Walter Mazzarri was under increasing pressure after an embarrassing FA Cup exit at Millwall and seven games without a win in the league.

But the visitors' energetic start - pressing Arsenal high up the pitch and not allowing the hosts time on the ball - created the platform for them to climb to 13th in the table, eight points clear of the relegation zone.

Central midfielder Capoue produced a dynamic performance. He contributed seven tackles and won the ball back the same number of times to top his team's defensive statistics and lay the groundwork for Watford's first league win over Arsenal in nearly 30 years.

Debutant M'Baye Niang, signed on loan from AC Milan until the end of the season, showcased his pace in the 70 minutes he was on the pitch and his strong running down the left caused Arsenal right-back Gabriel constant problems.