(Adds Puntland clash, NATO)

By Guled Mohamed

MOGADISHU, May 30 (Reuters) - A remote-controlled roadside bomb tore into an Ethiopian army convoy in Somalia on Wednesday, wounding five soldiers and sparking gunfire that killed at least four civilians, locals and a security source said.

Witnesses in the central Somali town of Baladwayne said they saw thick black smoke and injured soldiers covered in blood at the scene of the explosion -- the latest in a wave of Iraq-style insurgent strikes rocking the Horn of Africa nation.

"An Ethiopian truck was blown up," resident Osman Adan told Reuters by telephone. "The Ethiopian troops immediately opened fire indiscriminately with heavy machine-guns."

Adan said seven locals were caught in the cross-fire, but local journalist Ali Dahir said he had been able to verify four civilian fatalities.

"Two seriously injured soldiers were being removed from the truck. There was a lot of blood at the scene," Dahir added. "Nobody knows whether the Ethiopian soldiers died or not."

Ethiopian soldiers, in Somalia to help the government fight an insurgency led by militant Islamists, cordoned off the area after the blast and carried out door-to-door searches in nearby streets, witnesses said.

The security source in Mogadishu said one Ethiopian truck was destroyed by an anti-tank mine set off by remote control -- a new tactic being used by the insurgents.

"There were five troops on board. They were seriously wounded," said the security source, who asked not to be named.

IRAQ-STYLE TACTICS

Insurgents from the ousted militant Islamist movement have increasingly adopted the tactics of Iraqi guerrillas since the interim Somali government and its Ethiopian allies forced them out of the capital Mogadishu in December after a brief war.

The rebels have struck government buildings, convoys and Ugandan peacekeepers patrolling for the African Union (AU).

Most attacks have taken place in the seaside city, and local media said a Somali soldier was shot dead by unknown gunmen late on Tuesday near its sprawling Bakara Market.

On Monday, a senior court official from Baladwayne was also killed by gunmen in Mogadishu. His funeral was taking place on Wednesday in the town, 190 miles (300 km) north of the capital.

In another incident, official sources in the semi-autonomous north-east province of Puntland said two mid-sized boats had come to the Indian Ocean port of Barga on Wednesday. One offloaded some heavily armed Somalis and foreigners who fought with police on disembarking.

"As soon as they landed, there were heavy exchanges," a local police official told Reuters, speculating the group consisted of Islamists with foreign militant backers. It was not clear if there were casualties or how the clash had ended.

President Abdullahi Yusuf's government is struggling to impose central rule on the Horn of Africa nation, in anarchy since warlords kicked out dictator Mohamed Siad Barre in 1991.

Ethiopia says it wants its forces to leave once the AU force is up to strength, or at least at half its planned 8,000 troops.

But other African nations have been wary of sending more soldiers, especially after four Ugandan peacekeepers were killed two weeks ago by a roadside bomb targeting their convoy.

A NATO alliance officials said on Wednesday it was studying an AU request to provide air transport for its troops in Somalia as it has done in Sudan's Darfur region. "There is an intention among allies to help," he said.

( Additional reporting by Abdiqani Hassan in Bossasso, Mark John in Brussels)

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