Last updated on .From the section Republic of Ireland

Keane has not played for the Republic since replacing injured Shane Long against Poland in October

Republic of Ireland captain Robbie Keane's hopes of a quick return to action have been dashed after he underwent a knee operation which could rule him out for as long as six weeks.

The LA Galaxy striker missed both of the Republic's recent friendlies and he had surgery in the US on Thursday.

The Republic's five main strikers are all battling against injury.

Jonathan Walters, Kevin Doyle, Daryl Murphy are all currently ruled out while Shane Long also has a knock.

Keane's expected recovery timeframe should have him available for the friendlies against the Netherlands and Belarus but the 35-year-old's lack of football in advance of Euro 2016 may be a concern for manager Martin O'Neill.

Stoke's Walters will be out for around three weeks after undergoing knee surgery with Colorado Rapids forward Doyle likely to be missing for a similar duration after suffering a leg gash in the Republic's win over Switzerland last Friday.

Republic of Ireland's Euro 2016 Group E games 13 June v Sweden Saint-Denis, Paris 18 June v Belgium Bordeaux 22 June v Italy Lille

Ipswich striker Murphy picked up a calf strain against the Swiss after replacing Doyle while Long is battling to be fit for Southampton's game against Premier League leaders Leicester on Sunday because of a knee problem.

The Republic face the Netherlands and Belarus in friendlies on 27 May and 31 May before beginning their Euro 2016 campaign against Sweden on 13 June.

News of Keane's surgery was revealed on LA Galaxy's official website.

"LA Galaxy forward Robbie Keane underwent successful surgery on his right knee Thursday afternoon in Los Angeles," said the Major League Soccer club's statement.

"The surgery was performed by Dr Bert R. Mandelbaum at the Santa Monica Orthopaedic and Sports Medicine Group and Kerlan-Jobe Institute at Cedars-Sinai. The Galaxy captain is expected to miss four to six weeks."

Keane, 35, has not been a regular for the Irish over the past year but the country's record goalscorer has remained an ever-present in O'Neill's squad.

Keane has scored 67 goals in 143 internationals.

Newcastle goalkeeper Rob Elliot is out of the Republic's Euro 2016 campaign after suffering a serious knee injury in Tuesday's draw against Slovakia while Stoke defender Marc Wilson also faces a race against time to be fit for the finals.