GABORONE Oct 15 (Reuters) - Ten Eritrean soccer players seeking asylum in Botswana should be deported, Botswana's security minister said on Thursday, a decision their lawyer said he would challenge in court.

The Eritreans refused to board their plane home on Wednesday, the latest in a series of defections by athletes from a country under investigation by the United Nations for human-rights violations.

"The issue is simple: they must go back to their country. You don't come here to play football, lose, then say you want political asylum. There are proper steps that should be followed if you want to be a refugee," Defense and Security Minister Shaw Kgathi told GabzFM, a local private radio station.

Eritrean officials could not be reached for comment.

Dick Bayford, a lawyer representing the players, told Reuters he would file an urgent court application on Friday to prevent the government from deporting them.

The players are being kept at a police station in Botswana's second city of Francistown, where they played a match on Tuesday.

Similar mass defections by Eritrean soccer players occurred in Kenya in 2009, Tanzania in 2011 and Uganda in 2012. They were fleeing a country where slavery-like practices are routine and torture widespread, the United Nations said after a year-long investigation.

The investigation also found that Eritrea subjected its citizens to indefinite national service and killed people who try to flee the country, according to a U.N. report. The Eritrean Foreign Ministry dismissed the report without addressing specific allegations.

The Eritrean national team was in Botswana to play a World Cup qualifying match. Botswana won the game 3-1. (Writing by Ed Stoddard; Editing by James Macharia, Larry King)