(UPDATE) AP's reporter sent me a tweet saying "Even though the opening says "thousands", "10,000" is mentioned in the article and even the event with 200,000 people is mentioned in the article." Yes they are, and that's what I quoted below. I'm asking her why the opening was "thousands".
Photo from Mainichi, showing part of the crowd that may have been "several thousands" to "200,000" (Mainichi has 11 photographs of the protest at their site):
AP's Japanese reporter in Tokyo says "thousands" of people:
TOKYO (AP) — Thousands of people formed "a human chain" around Japan's parliament complex Sunday to demand the government abandon nuclear power — the latest in a series of peaceful demonstrations on a scale not seen in the nation for decades.
The reporter Yuri Kageyama notes later in the article that July 16 protest in Yoyogi Park drew "nearly 200,000" thanks to celebrities leading the pack, and says the Sunday crowd was smaller:
Similar demonstrations have been held outside the prime minister's residence every Friday evening. The crowds have not dwindled, as people get the word out through Twitter and other online networking. A July 16 holiday rally at a Tokyo park, featuring a rock star and a Nobel laureate, drew nearly 200,000 people.
The crowd appeared to be smaller Sunday. Kyodo News service estimated it at about 10,000 people. Participants said they came from across Japan, underlining the widespread appeal of the protests.
Reuters's foreign reporters in Tokyo says "tens of thousands", and also notes the defeat of an anti-nuclear candidate in the gubernatorial election in Yamaguchi Prefecture held on July 29:
TOKYO (Reuters) - Tens of thousands of people protested against nuclear power outside Japan's parliament on Sunday, the same day a proponent of using renewable energy to replace nuclear following the Fukushima disaster was defeated in a local election.
The protesters, including old-age pensioners, pressed up against a wall of steel thrown up around the parliament building shouting, "We don't need nuclear power" and other slogans.
On the main avenue leading to the assembly, the crowd broke through the barriers and spilled onto the streets, forcing the police to bring in reinforcements and deploy armored buses to buttress the main parliament gate.
The Metropolitan Police says (remember, there is no "official" number form the police on any demonstration) "ten and several thousands", according to Mainichi. TBS says "15,000", quoting their police source.
The organizers, who discouraged people from showing up on Friday to concentrate on the July 29 event, says "200,000". One of the organizers tweeted that she was going to focus on media handling (giving interviews) at the event, but did see the actual protest.
She was also tweeting about the Friday protest that she and her friends disapproved of, saying the number of 2,800 was "just about right", to which others responded by saying that was just too low.
The July 29 protest did produce two arrests. As Reuters and TBS News note, the protesters had a scuffle with the riot police when people flooded the streets, and two protesters were arrested for obstructing the police in the performance of their duties.
Interestingly, unlike the previous protests at the PM Official Residence on Fridays, BBC and NPR (National Public Radio in the US) have been reporting this particular protest repeatedly. I wonder if someone has gotten smarter and is contacting the foreign media to prompt better coverage.