A string of attacks killed five people and wounded more than 20 in eastern Libya on Wednesday, including in a stronghold of the internationally recognized authorities, officials said.

An interior ministry official said a suicide attack hit the center of Tobruk, a town close to the Egyptian border and 1,600 kilometers (1,000 miles) east of Tripoli that is the base of a contested parliament elected in June.

"At least one person was killed and 20 more injured, four seriously" in the suicide car bomb attack, a health ministry official said.

Witnesses said the "very powerful" blast caused extensive damage. Initial reports suggested there had been a double bombing.

Tobruk was also until recently the base for Prime Minister Abdullah al-Thani's government, which has moved its headquarters to the nearby town of Shahat.

The interior ministry official said the bombing did not strike near the hotel which houses parliament. But a lawmaker said security measures had been stepped up for fear of further attacks.

Another car bomb, also believed to be a suicide attack, struck near the Al-Abraq air base in eastern Libya, killing four soldiers and badly wounding another, officials said.

And in Benghazi, where deadly clashes between pro-government militias and Islamist fighters have raged for weeks, a package exploded in the city center, causing damage, witnesses said.

Both Libya's government and parliament took refuge in the remote east when Islamist-backed militias seized the capital in August.

The parliament was annulled by the Supreme Court last week but its anti-Islamist majority has refused to accept the judgement, saying it was handed down under duress.

Three years after dictator Moamer Kadhafi was toppled and killed in a NATO-backed revolt, Libya is awash with weapons and powerful militias, and run by rival governments and parliaments.