* Fighting continues near Goma in eastern Congo
* Congo army says it has pushed back M23 rebel thrust
* U.N. brigade backed Congo army in clash - spokesman (Adds details, French condemnation, analyst comment)
By Kenny Katombe
GOMA, Democratic Republic of Congo, Aug 23 (Reuters) - A special U.N. brigade formed to neutralise armed groups in Congo has taken its first military action, firing artillery at rebels menacing the border city of Goma, U.N. and Congolese military officers said on Friday.
The force of Tanzanian, South African and Malawian soldiers was backing the Congolese army against M23 fighters, whose brief occupation of the city last year damaged the image of the U.N. mission in Congo and led the Security Council to create the brigade.
The United Nations pledged in July to prevent the rebels from getting back within range of the city of about a million people on the Rwandan border.
But M23 this week entered a security zone ringing Goma that was established by the new, robustly-mandated Intervention Brigade earlier this month.
At least three people were killed on Thursday when shells landed on the city.
"Of course we responded with artillery as we cannot accept any threat to the population. That's why we retaliated," U.N. Lieutenant-Colonel Felix Basse told Reuters by telephone from Goma referring to Thursday's fighting.
Clashes between M23 and the Congolese army resumed early on Friday with peacekeepers again involved to hold back the rebels.
"Not just the Intervention Brigade but the complete MONUSCO force is acting to protect Goma," Basse said, adding that the army had by late afternoon taken territory from the rebels, including a strategic hill in Kibati, 11 km (7 miles) north of the city.
A Congolese army spokesman acknowledged the brigade was supporting government troops with artillery fire.
Meanwhile an M23 spokesman claimed the rebels were trying to avoid direct clashes but would respond to attacks.
"If the army carries on attacking us we're going to defend ourselves," Amani Kabasha said.
M23 has rejected responsibility for shelling Goma, but U.N. officials were quick to accuse the rebels of deliberately targeting civilians and U.N. positions. France followed suit.
" particularly condemns the attacks perpetrated by M23 against the civilian population and installations of MONUSCO, which constitute war crimes," a foreign ministry spokesman said on Friday.
READY OR NOT
Though it received its mandate in March, only around 2,000 of the Intervention Brigade's total force of 3,000 troops are currently in place in Congo and supplies and weaponry are still en route from contributing countries.
But Jason Stearns, director of the Rift Valley Institute's Usalama Project, said the force had little choice but to engage.
"The current fighting comes at a time of almost unparalleled pressure on the U.N. mission to do something. Unfortunately, it also comes before their Intervention Brigade is completely operational," he said.
The special brigade was established after M23 fighters marched past U.N. soldiers to briefly seize Goma last November.
The rebels withdrew after receiving promises of peace talks with the Congolese government. But the city's fall dealt a serious blow to the image of MONUSCO - with 17,000 troops the world's largest U.N. mission - and the U.N. is under pressure to ensure Goma is not retaken.
Some in the Intervention Brigade's contributing countries have voiced concern over their troops' daunting task of fighting and disarming rebel groups in the difficult terrain of Congo's volatile eastern borderlands.
A military spokesman in South Africa, which saw 14 of its soldiers killed in clashes with rebels in the Central African Republic in March, said South African troops had not been involved in clashes with M23.
"The fight is taking place near where our troops are positioned. We have a defensive line but we have not engaged," Siphiwe Dlamini said. (Additional reporting by Jonny Hogg in Kinshasa, Jon Herskovitz in Johannesburg and John Irish in Paris; Writing by Bate Felix and Joe Bavier; Editing by Andrew Roche)