DAKAR, June 28 Senegal deployed extra troops at ministry buildings, armoured personnel carriers near the presidential palace and at least one helicopter gunship in the capital Dakar on Wednesday after riots over lengthy power cuts.

Many Dakar homes and businesses have been without electricity for more than 30 hours, catalysing anti-government sentiment. Overnight, demonstrators burnt tyres and ransacked the offices of state electricity company Senelec and ministers' homes.

Riots erupted last week after President Abdoulaye Wade's tried to alter the constitution in a way his rivals said would make it easier for him to get re-elected in February.

Senegal has earned a reputation as West Africa's most stable and democratic country but is seeing rising public frustration over backsliding public services, particularly in power generation, since Wade took power in 2000.

Senelec director Seydina Kane, flanked by two ministers, said national television on Tuesday that the problems had been caused by fuel shortages and the company was working to get the situation back to normal by the end of the year.

"It is a difficult situation, Senelec would like to present its apologies to the entire population," Kane said.

Senelec has been unable to keep up with electricity demand for years and a source at the company said it was currently facing a "huge shortage of fuel". (Reporting by Diadie Ba; Writing by Bate Felix; Editing by Louise Ireland) (For more Reuters Africa coverage and to have your say on the top issues, visit: af.reuters.com/)