* Two militants killed, six captured in separate Sanaa raids
* Suspected of killing Frenchman, kidnapping Dutch couple
* Army offensive continues in south (Adds U.S. suspending embassy operations to public, paragraphs 4-5)
By Mohammed Ghobari
SANAA, May 7 (Reuters) - Yemeni security forces on Wednesday killed a prominent Islamist militant suspected of masterminding attacks on Westerners, including a French security agent gunned down two days ago, the country's supreme security committee said.
Security forces also detained five al Qaeda suspects and captured weapons in raids across the capital, the state news agency reported.
The announcements came as Yemeni forces pushed ahead with an offensive against al Qaeda in the Arabian Peninsula, or AQAP, and its local offshoot, Ansar al-Sharia, having captured the militants' main stronghold in the south on Tuesday.
Citing recent attacks against Western interests in Yemen, the United States suspended operations of its embassy in Sanaa to the public.
"We continue to evaluate the security situation every day, and we will reopen the embassy to the public once it is deemed appropriate," the State Department said in a statement on Wednesday, describing the step as "precautionary."
Yemeni officials say al Qaeda is behind a campaign of assassinations, including the killing of the Frenchman in Sanaa on Monday, to destabilise the U.S.-allied country as it tries to emerge from political turmoil following 2011 protests that forced veteran President Ali Abdullah Saleh to step down.
"Today, the government of Yemen announced the death of Wael al-Waeli, a terrorist ringleader - linked to AQAP - who planned and executed a number of criminal operations," the Yemeni Embassy in Washington said in a statement.
As well as the Frenchman's killing this week, it said Waeli was responsible for the kidnapping of a Dutch couple last year who were released in December after six months in captivity, an assassination attempt on a German diplomat last month and an attack on a Sanaa jail that freed over a dozen AQAP militants.
Special forces killed Waeli and another suspect as they left a house in Sanaa on Wednesday morning, it said. They arrested a third man.
Later on Wednesday, the Interior Ministry said security forces had captured five militants in various parts of the capital and found weapons and ammunitions used in the "terrorist attacks they implement in the capital," Saba news agency said.
Yemeni authorities accuse AQAP of involvement in dozens of attacks around the country, including a wave of assassinations of senior army and intelligence officers in drive-by shootings.
The level of retaliatory attacks against security forces has risen sharply since the start of the army offensive last week.
Gunmen shot dead a police officer in the southern province of Lahj, Saba reported on Wednesday. A local official in Lahj survived an assassination attempt by gunmen.
The army captured the southern town of al-Mahfad in Abyan province, one of two al Qaeda strongholds, on Tuesday and on Wednesday, the Defence Ministry said a number of "terrorists" in Shabwa - the other province where fighting is taking place - had been killed in clashes.
A military source said a militant commander known as Abu Dajana had been killed in the Shabwa fighting. Saba said security forces had also found the body of a militant known as Abu Ayyoub al-Jaza'iri (the Algerian) in Abyan.
Yemeni President Abd Rabbu Mansour Hadi has said many AQAP fighters in Yemen are foreigners. Yemen has announced the death of an Uzbek militant and a Chechen. (Additional reporting by Yara Bayoumy in Dubai, Mohammed Mukhashaf in Aden, and Peter Cooney in Washington; Writing by Sami Aboudi and Yara Bayoumy; Editing by Robin Pomeroy and Eric Walsh)