JERUSALEM, March 28 (Xinhua) -- Israeli tanks shelled two Hamas posts in the northern Gaza Strip on Wednesday morning after two Palestinians set fire near the fence between the Palestinian enclave and Israel.

The tanks targeted two observation posts belonging to Hamas, a Palestinian Islamist organization that runs Gaza, the Israeli military said in a statement.

Earlier, two suspects were seen setting fire to an elevated surface adjacent to the Karni Crossing, an old cargo terminal.

"The suspect did not cross the security fence and did not infiltrate Israel," the statement read. "The IDF (Israel Defense Forces) views with great severity any attempt to damage the security fence, as well as security infrastructure."

The incident came a day after three Gazans crossed into Israel and strolled for hours in southern Israel before they were caught and arrested. The army said they were armed with knives and grenades.

Tensions between Israel and Gaza were on the rise ahead of Friday, when mass demonstrations are expected to begin along the fence. Gazans plan to hold big marches towards the fence. The army said it will deploy 100 snipers authorized of using live fire to prevent attempts to cross the fence.