NAIROBI, Kenya — Extremist Muslims controlling much of southern Somalia declared jihad, or holy war, on Ethiopia yesterday after accusing its troops of capturing a town taken by the extremists last month.

The 750 Ethiopians were among forces loyal to the Somalia’s weak, transitional president, Abdullahi Yusuf. They seized Buur Hakaba without firing a shot early yesterday.

The Islamic Courts Union responded by stepping up their long-running threats to wage war with Ethiopia, which stands accused of sending thousands of troops into Somalia to defend Mr. Yusuf’s toothless administration.

“Starting from today, we have declared jihad against Ethiopia,” the union’s deputy leader, Sheikh Sharif Ahmed, said.

“Heavily-armed Ethiopian troops have invaded Somalia. They have captured Buur Hakaba,” he said. “History shows that Somalis always win when they are attacked from outside. We will counter them soon. I urge all the Somali people to wage holy war against the Ethiopians.”

Western governments fear that if reports persist of Ethiopian involvement in Somalia’s internal power wrangles, foreign jihadis will use Somalia as a battleground for Islam against the West.

Many Somalis view Ethiopia as a Christian imperialist power. There are unconfirmed reports of large-scale operations against ethnic Somalis living in Ethiopia’s southeastern Ogaden province, further inflaming the tense situation.