A suicide bomber has rammed an explosives-laden car into the military intelligence headquarters in a border town in Egypt's volatile Sinai, killing at least six and wounding 10, security officials said.

The bomber drove into the one-storey building in Rafah at high speed, collapsing its front part and burying an unspecified number of troops under the rubble, the officials said.

Simultaneously, militants fired rocket-propelled grenades at an army checkpoint near the building, the officials added.

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Militants in Sinai, some with links to al-Qa'ida, have been targeting Egyptian forces for months in the strategic peninsula bordering Gaza and Israel. Their attacks have become much more frequent and deadlier since the removal in July of Egypt's Islamist president Mohamed Morsi.

The Egyptian military earlier this week launched a major offensive against militants in the northern region of Sinai.

Officials have described the offensive, which started on Saturday, as the biggest sweep of the region in recent years, aiming to weed out al-Qa'ida-inspired groups that have taken control of villages in northern Sinai.

PA