* FA says UEFA not sending strong message on racism
* Serbian backroom duo banned for two years by UEFA
* Two England and four Serbia players suspended (Recasts after FA statement)
LONDON, Dec 13 (Reuters) - The English FA has criticised UEFA for not sending a "strong enough message" on racism after European soccer's ruling body fined Serbia 80,000 euros ($104,700) over incidents at an under-21 match in October.
The Serbian FA (FSS) was fined on Thursday and told it must stage its next under-21 home match behind closed doors after players and fans were found guilty of improper conduct.
The UEFA charges followed England's 1-0 victory in the European under-21 championship playoff in Krusevac when visiting full back Danny Rose complained he was racially abused by Serbia supporters before, during and after the game.
England scored with the last kick of the match and fighting broke out between players and officials immediately after the final whistle.
"We are disappointed with the sanctions levied by UEFA with regards to the racist behaviour displayed towards England's players," FA general secretary Alex Horne said in a statement.
"Let's be clear, racism is unacceptable in any form and should play no part in football. The scenes were deplorable and we do not believe the sanction sends a strong enough message."
A string of further punishments were disclosed earlier in a UEFA statement that made no mention of racism.
Serbia's assistant coach Predrag Katic and fitness coach Andreja Milunovic, who had already been suspended by the FSS for violating its ethics and fair-play code, were banned from football for two years by European soccer's ruling body.
UEFA also suspended four Serbia players. Goran Causic was banned for four international games, Ognjen Mudrinski and Filip Malbasic for three matches and Nikola Ninkovic for two.
Mudrinski and Ninkovic had already been suspended by the FSS for a year.
The FSS had denied the racism charges and said after the match that Tottenham Hotspur defender Rose, who is on loan at Sunderland, had provoked the home fans in an "inappropriate, unsportsmanlike and vulgar manner".
Serbia have long since had problems with racism and soccer violence.
They were forced to play a Euro 2012 qualifier behind closed doors after fans rioted and caused a senior international game against Italy to be abandoned in Genoa in 2010.
In June 2007, the FSS was fined 16,500 pounds ($26,600) because of racist chants and the behaviour of their fans at another under-21 match against England.
FSS secretary general Zoran Lakovic appeared to agree his organisation had got off lightly following this latest incident.
"The punishment is not as harsh as we thought it might be but the verdict and the incident that caused it should come as a last warning to everyone representing Serbian football," Lakovic said.
"That means the coaches, the players and of course the fans because even the slightest trouble in future could result in the most rigorous measures."
The fine of 80,000 euros is 20,000 less than UEFA fined Denmark striker Nicklas Bendtner at Euro 2012 for showing the logo of a betting company on his underpants while celebrating a goal.
England players involved in the post-match fighting in October were also punished by UEFA.
Defender Steven Caulker, who plays for Tottenham, was suspended for two international matches and Blackpool winger Tom Ince for one.
The sanctions provoked a frustrated response from England under-21 coach Stuart Pearce.
"I am concerned to see our players suspended by UEFA and we will continue to support them," Pearce said.
"I maintain our players played no part in the aggression. From what I witnessed our players and staff were forced to protect themselves in the violent scenes that followed the game."
($1 = 0.7641 euros) (Writing by Toby Davis; additional reporting by Alison Wildey and Zoran Milosavljevic; editing by Tony Jimenez)