Metal detectors for spectators will be installed along the entire marathon course at the world athletics championships in August as part of increased security following last week's Boston bombings, Russian organizers said.
"It definitely has given us an extra headache," long-serving Russian athletics chief Valentin Balakhnichyov said in reference to the blasts that killed three people and injured more than 200 at the Boston Marathon.
"The security will certainly be reviewed after what happened in Boston. Airports, hotels, the transit system, places where you have lots of people, are always vulnerable."
One of the ethnic Chechen brothers suspected of the Boston bombings made a visit last year to the volatile North Caucasus, where militant groups are fighting to establish an Islamist state.
In a wide-ranging interview, Balakhnichyov also emphasized Russia's tough stance on doping and confirmed that pole vault queen Yelena Isinbayeva planned to compete in Moscow.
Balakhnichyov said the capital would have a "triple level of protection" during the Aug. 10-18 championships.
"The first level would be the Federal Security Service and the police, then we have the city's own security personnel, and, finally, the security in and around the stadium," he said.
"Obviously, the marathon requires extra protection, not only for the runners but for spectators as well."
Men and women will race on an identical course, running alongside some of Moscow's most famous landmarks, including the Kremlin, and finishing at Luzhniki Stadium.
"The only way to guarantee sufficient security for those coming to watch the races is to install metal detectors along the entire 42.195-kilometer course," Balakhnichyov said.
"At the same time we don't want to make Moscow a ghost town. We must make sure that spectators, including foreign guests, are not scared away by overzealous policing.
"Luckily, the marathons are the only events held outside the Luzhniki sports complex. The rest, including race walking, will be held inside the complex," he added.
"Initially, we wanted to make Luzhniki an open zone, where people could just walk around, enjoy the atmosphere. Now, we'll have to reconsider it and have metal detectors there as well."
Filling the spacious Luzhniki stadium is the other major concern for the local organizers.
The championships will be the last international event taking place at Luzhniki. After that, the iconic arena, built in 1956 and named after Bolshevik leader Vladimir Lenin, will be closed for major renovations for the 2018 soccer World Cup.
The arena's capacity of 78,000 would be cut by half for the championships, Balakhnichyov said.
"The first 10 rows around the stadium will be empty because you have a limited view from there," he said.
A large part of the central tribune, opposite the VIP stand, would be covered by a huge screen, he added.
"If you take away seats occupied by TV commentators, print media and the VIPs, we'll have a capacity of about 35,000. I think this is a good target for us to fill all those seats."
During a visit to Moscow this month, International Association of Athletics Federations (IAAF) chief Lamine Diack criticized Russian organizers for failing to adequately promote the championships.
Balakhnichyov said preparations were going as planned.
"The new Mondo track has already been installed. The surface is exactly the same as was used at previous major championships, including last year's London Olympics, so we could see some really fast times, even world records.
"By the way, we've already set a new attendance record. We'll have more than 2,500 athletes from 205 countries competing in Moscow. It's more than London had because the Olympics use different quota criteria for athletes," he said.
Next month, Luzhniki's synthetic pitch will be replaced with turf, Balachnichyov said.
"We're a bit worried that rugby players will destroy the grass during their event [Sevens World Cup] in late June. In that case, the pitch will be re-laid anew."
He said Isinbayeva, Russia's biggest name in athletics, had no plans to retire and would compete in Moscow.
"I talk to her regularly on the phone, so I'm keeping close tabs on her preparations. Believe me, she has enough motivation to continue her sporting career," Balakhnichyov said.
Asked if Isinbayeva, who turns 31 in June and has not competed since the London Olympics, would be guaranteed a spot on the team without having to qualify, he smiled.
"We can't afford not to have Yelena competing in Moscow. She is our biggest draw along with [Jamaican sprinter Usain] Bolt. The days they compete will definitely be sold out," he said.
Balakhnichyov emphasized Russia's tough stance on doping, saying his country had conducted more drugs tests than any other country in the world in the last couple of years, but had been wrongly singled out for being too soft on drug cheats.
The Russians have come under heavy scrutiny after nearly two dozen of their leading athletes failed tests in the past 12 months.
"Some nations only do 500 tests a year. We did 3,500 tests last year alone, and this year we plan to do over 4,000 tests in and out of competition," he said.
"Statistics show that drug cheats account for about 1 or 2 percent of those who were tested. These figures are more or less the same for most leading nations in our sport, which means if we do 4,000 tests a year we could have nearly 80 athletes test positive. The rest of the world will look at these numbers and say 'Russians are cheating.' And that's not fair!"