Mogadishu, Somalia ? A mysterious Russian-built cargo plane believed to be loaded with weapons landed in this capital Wednesday, setting off a fresh round of allegations that Somalia has become a proxy battleground for its neighbors Eritrea and Ethiopia.

The United States and other Western powers have cautioned outsiders against meddling in Somalia, which has no single ruling authority and can be manipulated by anyone with money and guns. But there’s little sign the warning has been heeded.

Somalia’s virtually powerless government charged on Wednesday that the Ilyushin-76, only the second flight to land at Mogadishu International Airport in a decade, was packed with land mines, bombs and guns. It said the shipment had come from Eritrea, which supports the Islamic militia that has seized the capital along with most of southern Somalia.

Just hours later, a U.N. envoy confirmed that troops from Ethiopia, Eritrea’s foe, were in Somalia to protect the defenseless government from the advancing Islamic forces.

Ethiopia and Eritrea fought a bloody border war from 1998-2000, and have since backed rebel groups to destabilize each other. Somalia could become a new front in their conflict.

Somalis in Mogadishu look from a distance at the Ilyushin-76 plane that landed at the capital's airport. Somalia's virtually powerless government said the plane was carrying weapons for Islamic militants who have seized control of much of southern Somalia.

“Ethiopia and Eritrea are competing throughout the region, opening up new fronts in their Cold War whenever the opportunity arises,” said John Prendergast, a senior adviser with the International Crisis Group, which monitors conflict zones.

The United States also has been involved in Somalia. It secretly backed nonreligious militias that were driven out of Mogadishu by the Islamists, and now supports the government.

The United States has accused the Islamic militia of ties to al-Qaida, whose leader, Osama bin Laden, called for support of the militia in a recent recording. The Associated Press also recently obtained videotape of Arab Islamic fighters alongside Somali militiamen.

“There are external parties involved on all sides,” said Jendayi Frazer, the U.S. State Department’s top Africa official. “This is a problem.”