MANILA (Reuters) -- Muslim gunmen in the Philippines freed three local engineers and their driver working on a U.S.-funded road project on a remote southern island after abducting them three days earlier, the military said on Friday.

Lieutenant-Colonel Bartolome Bacarro said the four men were found by soldiers just after dawn on Friday walking on a jungle trail near Indanan town on Jolo island, the stronghold of the Abu Sayyaf group of Muslim rebels.

"They were tired but appeared to be in good shape," Bacarro told reporters, adding military pressure helped local officials convince the gunmen to free their captives.

Six gunmen snatched the men late on Tuesday while they were inspecting the project near Parang town on Jolo and demanded an unspecified "board and lodging fee".

Benjamin Loong, governor of the troubled southern island, said the captives were freed without conditions after ransom demands were rejected. He said relatives of the kidnappers also helped in the negotiations.

But one of the four captives said they had escaped after a guard fell asleep late on Thursday and then they walked through the night until soldiers found them the next day.

"We were tied to each other and were not fed for two days," said Isidro Amaramo, the driver of the three engineers, showing bruises after he was hit by a rifle butt.

Security officials said the kidnappers withdrew money from banks in Zamboanga City using five ATM cards taken from the engineers, but there was no immediate estimate of how much money was taken.

Local police said one of the suspected kidnappers was related to the head of a private security group hired to guard the 3.6-km (2.2-mile) road project funded by the U.S. Agency for International Development (USAID).

Taking hostages for ransom is relatively common in the southern Philippines, one of the poorest parts of the mainly Roman Catholic country due to a long-running separatist conflict between minority Muslims and the central government.