Updated

United Nations troops in the Democratic Republic of Congo went into action Friday to battle M23 rebels accused by France of war crimes after clashes near the flashpoint city of Goma that left at least four dead.

Late Thursday, shells hit the outskirts of the eastern city, killing a woman and a child, and a rocket struck the nearby village of Kanyaruchinya, killing two and injuring nine others, according to the UN.

The civilians were victims of fighting that has erupted sporadically since mid-July between M23 and the regular army in a region 20 kilometres (12 miles) north of Goma, a city of one million people, ending a truce of about two months.

France "condemned" the surge in fighting and "in particular attacks perpetrated by the M23 against civilians and the United Nations mission in the country (MONUSCO) which constitute war crimes", said foreign ministry spokesman Vincent Floreani, urging UN troops to use "all disposable means" to defend the local people.

UN military spokesman Prosper Basse told UN-sponsored Radio Okapi that MONUSCO troops were "henceforth engaged alongside the FARDC (regular army)" to deal with the threat.

It marks the first time the UN brigade has fought alongside the army.

MONUSCO had already declared a protection zone with a perimeter of 30 kilometres (19 miles) around Goma and the nearby strategic town of Sake three months ago "to prevent this sort of atrocity by M23 against civilian populations", spokesman Basse said.

The Kinshasa government has accused Rwanda of firing the rockets on Goma on Thursday, to help the M23, whom Kigali is suspected by some of supporting.

"The DR Congo government is awaiting an explanation from its neighbour over these serious events," said spokesman Lambert Mende.

In a tit for tat exchange, Kigali accused the Congolese army of launching a rocket on Rwanda while the DR Congo said that M23 rebels had done it to implicate the government, and provoke conflict with Rwanda.

M23 meanwhile issued a statement laying the blame on the regular army and an ethnic Hutu rebel movement based in the region, the Democratic Forces for the Liberation of Rwanda (FDLR).

They had dropped "several bombs on Rubavu district in... Rwanda and central Goma to get Rwanda and MONUSCO involved in the war" said the M23.

With the UN brigade -- authorised in March to take the offensive against armed movements -- moving into action, South African artillery forces destroyed a rebel T55 tank stationed near Kibati, about 20 kilometres (12 miles) from Goma, according to the UN. South Africa's defence ministry however denied that its troops were directly implicated.

Meanwhile President Jacob Zuma of South Africa, which has committed 1,345 men to the UN brigade, met in Luanda with DR Congo President Joseph Kabila and Angola's Jose Eduardo dos Santos to discuss the insurgency.

Dos Santos said the instability threatened "the peace and security of the whole region".

M23 is made up of Congolese Tutsi former rebels who were integrated into the army following a 2009 peace accord. They mutinied in April 2012 saying the agreement was never fully respected by the Kinshasa government.

UN experts have accused neighbouring Rwanda and Uganda of backing the rebel movement, a claim both countries refute.

The insurgents occupied Goma for 10 days last November before withdrawing under international pressure and in return for a dialogue with Kinshasa, which has since stalled.