A further 21 cases of polio have been found in Indonesia, bringing the total to 100, the WHO has said.
Indonesia has begun mass immunisation campaigns
Twenty of the new cases are in Banten, West Java, the location of the first case in the current outbreak.
The other new case is on the island of Sumatra, which was polio-free until last week.
Officials believe the outbreak can be traced to Nigeria, where vaccinations were suspended in 2003 after radical clerics said they were a US plot.
Tuesday's information brings the number of polio cases on Sumatra to two - the first was confirmed last week. Both are in the province of Lampung. They are of concern to the WHO because they suggest the disease has jumped islands, WHO spokesman Oliver Rosenbauer said.
All other cases have been limited to Java.
Mr Rosenbauer said Sumatra would also take part in the next phase of a mass immunisation drive, planned for early August.
Indonesia first detected a case in West Java province, 120km (75 miles) east of the capital, Jakarta, in April.
Indonesian officials say the virus could have been picked up by a pilgrim on the hajj to Mecca, or a migrant worker.
Polio is still endemic in six countries - Afghanistan, Egypt, India, Nigeria, Niger and Pakistan.
The United Nations has been campaigning to eradicate the disease by the end of this year.