Manchester, Mar 10 (IANS); Manchester City extended their lead at the top of the English Premier League to four points after a hat-trick from forward Raheem Sterling saw them beat Watford 3-1 here.

Sterling's first goal in the 46th minute at the Etihad Stadium here on Saturday evening was highly contentious.

Sterling was clearly offside when Sergio Aguero played the ball to him before Watford full back Daryl Janmaat's challenge saw the ball ricochet off the England forward into the goal, reports Efe news.

The assistant referee raised his flag for offside, but after a lengthy discussion without the use of the Video Assistant Referee (VAR), the goal was allowed to stand.

City's second goal came just four minutes later when Sterling tapped in from Riyad Mahrez's cross from the right.

City were rampant and the game was effectively settled less than 10 minutes later when the England winger completed his hat-trick with a cool finish past Ben Foster after being played in by David Silva's clever reverse pass down the left.

"I am sorry if (the first goal) is offside but we deserve to win", City coach Pep Guardiola, who praised his side's perseverance, said after the game.

Watford manager Javi Gracia rued his players' loss of concentration following Sterling's controversial opener, although the Spaniard refused to criticise the referee for what he called a "clear" error.

Watford remains on course for their best-ever top flight finish, while City ended a difficult week, which saw various football bodies, including the Premier League, UEFA and FIFA, open investigations into their player recruitment processes and financial affairs.