Small-arms and artillery fire broke out early Friday around the capital of Rwanda as foreign troops arrived, six days after a rebel force invaded from neighboring Uganda, according to radio reports.

The source of the gunfire was not immediately clear.There also were unconfirmed reports an airliner carrying French Foreign Legion troops to Rwanda was fired on while landing at the international airport in Kigali, the nation's capital.

The rebels, Rwandan refugees predominantly of the minority Tutsi tribe, invaded across the northern border with Uganda on Sunday. Many deserted from Uganda's army. Estimates of the size of the invading force have ranged from several hundred to several thousand.

Rwanda's government Friday repeated broadcasts every half hour on state-run radio urging most people to stay indoors. The government warned residents of "the situation of insecurity now prevailing in our country."

Officials declared gatherings of more than two people illegal and barred unauthorized travel. A nighttime curfew remained in effect.

Residents in Kigali said gunfire broke out in and around the capital about 2:20 a.m.. They reported hearing shellfire on the city's outskirts, according to the BBC.

On Wednesday, a diplomatic source said Rwanda's army had stopped the main rebel force at Gabiro, about 40 miles northeast of Kigali, with helicopter-borne rocket and cannon fire. An army officer in Uganda also reported heavy bombing by the Rwandan army.

However, a group of 100 to 200 guerrillas was seen near Lake Muhazi, about 30 miles south of Gabiro and east of Kigali, according to the diplomatic source.

Belgium, Rwanda's former colonial power, sent an unspecified number of troops and military equipment at the request of Rwanda's president, Juvenal Habyarimana. An unconfirmed report on Belgian radio said 200 paratroopers had been sent.

Habyarimana, of the majority Hutu tribe, has ruled Rwanda since seizing control in a bloodless 1973 coup.

The rebels seek Habyarimana's ouster but deny they are bent on ethnic revenge.