PRESS ASSOCIATION -- Syrian troops have stormed parts of the eastern city of Deir el-Zour and explosions can be heard throughout the area, according to activists.

An activist said the military launched a pre-dawn raid on the city, attacking it from four sides and so far taking control of eight neighbourhoods.

On Saturday, Syrian forces tightened a siege on the city of Hama, the main centre of the nearly five-month-old uprising against President Bashar Assad's regime.

The activist said the military raid on Deir el-Zour began at 4am on Sunday morning. The activist spoke on condition of anonymity, fearing reprisals.

The Local Co-ordination Committees, an activist group tracking the uprising, confirmed parts of the city were taken over by troops.

There was no immediate word on casualties.

Earlier the country's foreign minister tried to defuse protests by promising free elections by the end of the year.

Like previous reform promises, the new announcement is unlikely to have much resonance with Syria's opposition, which says it has lost all confidence in President Bashar Assad's overtures.

The four-year term of the current parliament expired earlier this year and Assad is expected to set a date for new legislative elections before the end of 2011.

Foreign minister Walid al-Moallem pledged to press ahead with reforms and said the new parliament "will represent the aspirations of the Syrian people".