DAMASCUS, June 2 -- Syria has beefed up security in and around the capital Damascus just one day before the first multi-candidate presidential poll in the country's modern history.

Checkpoints at Damascus' entrances have further tightened inspection measures, while the authorities have secured the government establishments and areas where polling stations and booths were setup.

Syria's Interior Ministry said on Monday that it was taking all required procedures to facilitate citizens going to and coming from city centers for the polling.

The intensive security measures come as the opposition rebels were threatening to launch attacks against polling stations in the capital to disrupt the vote, as has been revealed in some of their statements on the Internet.

"We announce the commencement of targeting the security headquarters, the polling stations, their committees and members as of Tuesday, June 3, and thus we ask the citizens to stay away from the mentioned areas," one statement read.

"We declare Damascus a military zone until the end of the filthy elections," another said, warning people to stay away from polling stations which had been considered by the rebels as " legitimate targets."

On Monday the rebels on Damascus suburbs fired several mortar shells that targeted all but security headquarters. The mortars landed near the Faculty of Art of the Damascus University and in many other residential areas, causing injuries and property losses.

Despite all the threats, the Syrian government seemed to have taken all necessary measures to secure the voting process, amid reports that public transportation is free on Tuesday to serve those who want to reach the polling stations.

The Interior Ministry said that more than 15 million eligible and registered voters are expected to cast their ballots at 9,610 polling stations across Syria.

Meanwhile, the state news agency SANA said that delegations of expat Syrians are arriving in Syria to participate in the vote. Those expats could not cast their ballots during the overseas polling in late May, because Syrian embassies in their living countries had been banned to hold the voting.

Tuesday's presidential election is the first one in half a century. Before that Syria only had referendums to support President Bashar al-Assad or his late father Hafez al-Assad who was in office from 1971 to 2000.