MANAUS, June 18 -- Cameroon's World Cup campaign sunk into ignominy on Wednesday when Benoit Assou-Ekotto head-butted teammate Benjamin Moukandjo during their 4-0 loss to Croatia.

The pair had to be separated by striker Pierre Webo after clashing in the 90th minute of the one-sided encounter at the Amazonia Arena stadium.

After the match a furious Cameroon coach Volker Finke vowed to find he cause for the incident.

"It's clear we have to find the reasons what's going on because such behavior is really disgusting, it won't do, it's impossible," Finke said.

Earlier, midfielder Alex Song was shown a straight red card for elbowing striker Mario Mandzukic in the back.

Wednesday's result means the Indomitable Lions are eliminated from the tournament despite a group match against Brazil to come.

Cameroon's disastrous campaign follows a series of off-field controversies that blighted their preparations for football's showpiece event.

The squad almost refused to board a flight to Brazil over a pay dispute while their star striker Cameron Eto'o has faced allegations about his personal life.

At a press conference on Tuesday, Eto'o vowed to "respond to all accusations" and "reveal names" after the World Cup.

The capitulation against Croatia was Cameroon's sixth straight World Cup loss.

The have managed just one World Cup victory - a 1-0 defeat of Saudi Arabia in 2002 - since becoming the first African nation to make the tournament's quarterfinals in 1990.