NAIROBI, May 30 (Reuters) - Somali pirates fired rockets as they seized two freighters off the lawless Horn of African coast bringing to three the number of ships hijacked this week, a Kenyan maritime official said on Friday.

"The two ships were hijacked on Wednesday," Andrew Mwangura, head of the Kenya-based Seafarers Assistance Program, told Reuters.

"We do understand that the pirates on board two fast boats fired rockets at the ships. The number of crew on the ships are still unknown," he said.

Hijackings are common in the chaotic country's un-patrolled waters, where pirates normally treat hostages well in anticipation of hefty ransoms.

He said there was little information available on the seized vessels -- Arean and Lehmann Timber -- other than where they were registered and who their owners were.

Local officials said the two ships were commandeered towards the Ras Bina area in the relatively peaceful Puntland region where pirates were also holding a Dutch-owned ship seized over the weekend along with its Russian and Filipino crew.

Somalia has been mired in anarchy since the 1991 ouster of a dictator.

An interim government formed in 2004 struggles to assert its authority but is facing an Iraqi-style Islamist insurgency in the capital Mogadishu and elsewhere.

In the latest of such attacks, residents of the south-central town of Baidoa, 245 km (152 miles) southwest of Mogadishu, said on Friday suspected Islamists hurled a grenade at a house belonging to a lawmaker in the interim government, badly wounding his family.

The legislator was not in the house at the time of the attack.

"We received 10 wounded people mostly children including the lawmaker's wife. The mother and three children are in serious condition. The rest are stable," Abdikadir Bare, a doctor in a Baidoa hospital where the victims were taken told Reuters. (Reporting by Aweys Yusuf in Nairobi and Mohamed Ahmed in Baidoa; Writing by Guled Mohamed; Editing by Matthew Jones) (For full Reuters Africa coverage and to have you say on the top issues, visit:http://africa.reuters.com/)

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