LONDON — Britain believes there are between 10,000 and 13,000 Islamic State fighters active in Iraq, Foreign Secretary Philip Hammond said Tuesday.

Hammond added that excluding Islamic State and Al Nusra fighters, he believed there also were some 80,000 opposition fighters in neighboring Syria.

“It is estimated … that there are 10,000 to 13,000 active ISIL fighters in Iraq,” he told lawmakers, using a different title for Islamic State.

Asked about Syria, he said: “The non-ISIL, non-al-Nusra part of the opposition probably amounts to around 80,000 fighting strength deployed across the country — that is the latest estimate that I have,” he told lawmakers.