New Delhi, Jan 26 (IANS) The airspace over the capital was closed, anti-aircraft guns were positioned at strategic locations and more than 15,000 security personnel, including snipers, spread out Friday to prevent any terror attack on Republic Day.

"There are intelligence inputs that militants could try to disrupt the Republic Day parade, so the city has been put on high alert," a senior police official said.

Most roads in central Delhi were heavily guarded with snipers being positioned in key positions.

In addition, about 400 commandoes of the Delhi Police were positioned from Vijay Chowk to Red Fort. Anti-aircraft guns and mobile hit teams were also deployed.

In other parts of the city, barricades were erected and vehicles stringently checked. Unwilling to take a chance, Delhi Metro also closed service - and their parking lots. Other parking lots in the city were checked too.

Delhi Police had Thursday arrested a suspected Lashkar-e-Taiba terrorist from the capital with 2.5 kg RDX, detonators and timers. Two Kashmiri militants had been arrested earlier in the week.

"Random checks of vehicles at police barricades had started on the eve of the Republic Day itself. Spotters have been deployed at airports and we are keeping a close watch on several parts of the old Delhi area," said a police official.

All vehicles entering Delhi from the other states were being checked.

"In addition to the area around the parade route, security was also tightened at all prominent government installations," he said.

Delhi Police teams conducted patrolling in the sensitive area and security was tightened at railway stations and inter-state bus terminals.