By Elias Biryabarema

KAMPALA (Reuters) - Uganda rejected on Tuesday charges by rights group Amnesty International that its security forces carried out extra-judicial killings during clashes with the royal guards of a tribal king at the weekend.

Officials say at least 46 guards and 16 police died when the security forces stormed the palace of Charles Wesley Mumbere, king of the Rwenzururu kingdom, near Uganda's border with Congo. Mumbere was detained and has now been charged with murder.

"Security forces were being attacked. They had to defend themselves, they had to protect themselves," Jeje Odongo, Uganda's internal affairs minister, told a press conference in the capital, Kampala.

"Security agencies ... do not have a shoot-to-kill policy. What happened is a situation of self-defense."

Uganda has several tribal kings, who have a largely ceremonial role with some modest regional powers.

The latest unrest started shortly after Uganda's disputed presidential elections in February. Voters in the area overwhelmingly favored Kizza Besigye, who ran against long-ruling President Yoweri Museveni.

Museveni was declared the winner, but Besigye rejected the results and his supporters insist he won the overall poll.

On Monday, Amnesty International accused security forces of using disproportionate force, saying "many people appear to have been summarily shot dead".

The rights group said the government should ensure that "police and soldiers observe restraint and desist from extra-judicial executions."

International rights watchdog Human Rights Watch also said on Monday that the government needed to investigate the conduct of security forces during the clashes.

Some opposition officials and critics have accused Museveni's government of provoking unrest in the region as punishment for its support for Besigye.

Mumbere, who was detained by security on Sunday after his palace was stormed, was charged with murder on Tuesday and transferred to prison until Dec. 13, when he returns to court, according to Solomon Muyita, spokesman for Uganda's judiciary.

Since his arrest he had been held at a prison in Jinja, a town in eastern Uganda.

Odongo told the press conference 149 of Mumbere's guards had also been arrested following the clashes.

(Editing by Katharine Houreld and Hugh Lawson)