On Tuesday Rwandan troops crossed into eastern Congo in a joint military operation by the Great Lakes neighbors to disarm Rwandan Hutu rebels seen as a root cause of more than a decade of conflict.

Both governments presented the operation as a move to finally pacify the east of Democratic Republic of Congo, where fighting flared again late last year during an advance by Tutsi insurgents who are sworn enemies of the mostly Hutu Democratic Forces for the Liberation of Rwanda (FDLR).

Analysts said allowing the Rwandan forces in was a risky strategy for Congolese President Joseph Kabila, whose government army has often been accused by critics of using the FDLR to fight armed opponents and keep Tutsi-led Rwanda at bay.

The European Union, however, called the operation a tangible sign of improved relations between the two countries.

The presence of the FDLR, who finance themselves by exploiting illegal mines in the mineral-rich east, triggered two previous Rwandan invasions of Congo that led to a wider 1998-2003 conflict. It also helped cause a 2004 rebellion by Congolese Tutsi rebels who went on the offensive in October.