Twenty-five people have been killed and 175 wounded in two explosions that targeted security compounds in the northern city of Aleppo, Syrian media reports.

State television blamed "terrorists" for the blasts, following the regime line that armed groups looking to destabilise Syria are behind the uprising. Opposition activists accused President Bashar Assad's regime of setting off the explosions.

The blasts were the first significant violence in Aleppo, Syria's largest city, which has largely stood by President Bashar Assad during the nearly 11-month-old uprising against his rule. The TV quoted the Health Ministry in giving the casualty figures.

Anti-Assad activists accused the regime of setting off the blasts to discredit the opposition and to overt protests that had been planned in the city on Friday. Two earlier bombings in Damascus in December and January that killed dozens prompted similar exchanges of accusations. There has been no claim of responsibility for any of the attacks.

Outside the compound of the Military Intelligence Directorate, hit by one of the morning explosions, a weeping corespondent on state-run TV showed graphic footage of at least five corpses, collected in sacks and under blankets by the side of the road.

Debris filled the street and residential buildings appeared to have their windows shattered. But the location did not appear to be closed off, as local residents milled around the site, with few uniformed police around.

No emergency vehicles or ambulances were visible in the footage and there was no sign of wounded, as earth-moving equipment was seen clearing the rubble.

The presenter said the blast went off near a park where children were playing and claimed children were also killed. Although it lingered over the adult bodies, the TV footage did not show any child victims.

So far, Assad's opponents have had little success in galvanising support in Aleppo, in part because the business leaders have long traded political freedoms for economic privileges. The city of around two million also has a large population of Kurds, who have mostly stayed on the sidelines of the uprising since Assad's regime began giving them citizenship, which they had long been denied.

In another development, Syrian troops who for the past six days have been bombarding the city of Homs made their first ground move of the campaign to seize one of the city's restive neighbourhoods.