GENEVA, Jan 30 (Reuters) - Thousands of people have fled their homes and more could soon follow as a result of a new military offensive in the Democratic Republic of Congo, the United Nations refugee agency said on Friday.

The U.N. High Commissioner for Refugees (UNHCR) said that tensions have grown in Congo's South Kivu province since last week's start of a Congolese-Rwandan operation to crush Rwandan Hutu rebels in North Kivu.

About 5,000 people fled the Makobola area in South Kivu after a militia opposing the joint offensive blocked a main road there, UNHCR spokesman Ron Redmond said.

And some 1,300 Congolese refugees have crossed into Uganda to flee fighting in North Kivu in the past four days, with more expected in their wake, he told a news briefing in Geneva.

"The majority of them are women and children," Redmond said. "We are concerned that the growing tensions and the blockage ... could force more displacement."

In an abrupt turnaround in diplomatic relations between the two Great Lake neighbours, former foes during a 1998-2003 war, Rwanda sent more than 3,500 soldiers across the border last week at the invitation of the Congolese government.

The alliance to root out the Hutu rebel Democratic Forces for the Liberation of Rwanda (FDLR) has been touted by both as an effort to end a lingering conflict and humanitarian disaster that since 1998 has killed an estimated 5.4 people.

But U.N. human rights officials have warned that the offensive could trigger further displacement unless civilians in the area are properly shielded from renewed fighting.

Redmond said that increasing numbers of Rwandans living in Congo's South Kivu have been seeking to return home in recent days, with many asking for repatriation assistance.

And he noted that Makobola -- where the Mai Mai militia had blocked the road -- is a destination for Congolese refugees returning home from exile in neighbouring Tanzania after previous conflicts, meaning their path may be disrupted. (Reporting by Laura MacInnis)

AlertNet news is provided by