U.S. and Iraqi forces battling Shi'ite militias in Baghdad have killed at least 17 militants.

The military says militia fighters fired several rockets in the Iraqi capital. One of the rockets hit the office of the British Broadcasting Corporation in central Baghdad, causing structural damage but no injuries.

Health officials say they received four bodies and treated 51 people wounded in clashes since Thursday. It is not clear if any militants were among them.

Fighting in the capital has intensified since late March, when Iraqi Prime Minister Nouri al-Maliki ordered a crackdown on Shi'ite militias.

In other news, U.S. military officials in Iraq said earlier Friday the leader of al-Qaida in Iraq has not been captured -- denying Iraqi Interior Ministry reports Thursday that Abu Ayyub al-Masri had been detained in a raid in the city of Mosul.

Al-Masri, who also goes by the name Abu Hamza al-Muhajir, took over command of al-Qaida in Iraq after Jordanian militant Abu Musab al-Zarqawi was killed in a U.S. air strike in 2006.

Last year, Iraqi forces said al-Masri had been killed in fighting, but al-Qaida in Iraq denied that report and released an audio recording from the Egyptian-born militant.

Last month, a message said to be from al-Masri threatened a fresh campaign of attacks against U.S. troops and vowed to behead a U.S. soldier.

Some information for this report was provided by AFP, AP and Reuters.