UNITED NATIONS, May 29 (Reuters) - U.N. peacekeeping chief Herve Ladsous said on Tuesday that militia supporting Syrian President Bashar al-Assad were probably responsible for killing people with small arms and knives in the massacre of 108 civilians in Houla.

"Part of the victims had been killed by artillery shells, now that points ever so clearly to the responsibility of the government. Only the government has heavy weapons, has tanks, has howitzers," Ladsous told reporters.

"But there are also victims from individual weapons, victims from knife wounds and that of course is less clear but probably points the way to the (pro-Assad) shabbihas, the local militia," he said. (Reporting by Louis Charbonneau and Michelle Nichols; Editing by Sandra Maler)