ISMAILIA, Egypt, Nov 25 (Reuters) - Militants bombed security bases being built in Egypt's Sinai Peninsula, injuring three people, authorities said, as the state tries to reassert control over territory that slipped from its grip after the uprising that toppled Hosni Mubarak.

A massive explosion partly destroyed the wall of a security base being built for border guards in the town of Rafah at the border with the Gaza Strip overnight, but without causing injuries.

Further south, three workers were injured by a separate blast that damaged a compound being built in Quseima for a different security agency responsible for guarding a pipeline that exports gas to Jordan, security sources said.

Hardline Islamist militant groups have expanded into a vacuum left by the collapse of state control in North Sinai during the uprising that overthrew Mubarak in February, 2011.

The state launched a concerted effort to reestablish control following an Aug. 5 attack in which 16 border guards were killed. But a Nov. 3 gun attack in which three policemen died underlined the challenge still facing the authorities. (Reporting by Yousri Mohamed; Writing by Tom Perry; Editing by Andrew Roche)