NAIROBI – Kenyan security forces were locked in a fierce, final battle with Somali Islamist gunmen inside an upmarket Nairobi shopping mall on Monday as huge explosions and a barrage of heavy gunfire echoed out of the complex.

A thick cloud of black smoke billowed out from the Westgate mall as Kenyan officials said the 50-hour-long siege — which has seen the gunmen massacre at least 69 people and take dozens more hostage — was close to being resolved.

“We think the operation will come to an end soon,” Interior Minister Joseph Ole Lenku told a press conference. “We are in control of all the floors; the terrorists are running and hiding in some stores . . . there is no room for escape.”

Four large blasts rocked the Westgate Mall on Monday morning, sending large plumes of smoke over the upscale Nairobi suburb as Kenyan military forces moved in to rescue hostages held by al-Qaida-linked militants.

The explosions were followed by volleys of gunfire and a thick, dark column of smoke. Military and police helicopters and a plane circled over the mall, giving the Westlands neighborhood the feel of a war zone.

At least two of the terrorists were killed in the assault and there were “several injured,” Lenku added.

In the meantime, hostages continued to be held despite an earlier statement from the military that “most” had been rescued, a source said Monday. Another 63 people are listed as missing, the Kenya Red Cross said the same day.

Somalia’s al-Qaida-linked Shebab insurgents have taken credit for the attack, which began Saturday, but Kenyan army chief Julius Karangi said the gunmen had different nationalities. He did not elaborate.

“They are from different countries. We have sufficient intelligence this is global terrorism,” Karangi said.

Several foreign fighters, including Somalis with dual nationalities, are members of the Shebab force.

Contrary to some earlier rumors, Lenku denied that any of the insurgents were women.

“There are no women, all the terrorists are men. Some of them had dressed like women,” he said.

The 63 recorded missing were thought to include both hostages still being held by militants fighting troops in the complex, as well as those possibly killed in the three-day siege.

Others may be hiding in the sprawling shopping center.

Military helicopters circled over the mall at daybreak, when about five minutes of sustained gunfire broke out inside Westgate Mall, a clear indication that at least one of the estimated 10 to 15 gunmen who attacked the mall when it was filled with shoppers Saturday was still on the loose. More gunfire rang out later, much as it did throughout the day Sunday.

Late Sunday a military spokesman said that “most” of the hostages had been released. But a source with knowledge of the rescue operation said that no hostages had been released or rescued overnight. The person insisted on anonymity in order to talk about the rescue response.

Another indication no hostages had been freed: None appeared at the Oshwal Center, a squat concrete structure that houses a Hindu temple just next to the mall that the Red Cross is using as a triage center. Medical workers attended to at least two wounded Kenyan soldiers there Monday.

From Somalia, Sheik Ali Mohamud Rage, a spokesman for al-Shabab — the militant group that claimed responsibility for the attack — said in an audio file posted on a website that the hostage takers had been ordered to “take punitive action against the hostages” if force was used to try to rescue them.

Al-Shabab militants reacted angrily to the helicopters hovering over the mall, and warned on Twitter that the Kenyan military action was endangering hostages.

On Sunday, Kenya’s military launched a major operation against the militants

The military assault began shortly before sundown, with one helicopter skimming very close to the roof of the shopping complex as a loud explosion rang out, far larger than any previous grenade blast or gunfire volley.

Kenyan police said on Twitter that security forces had launched a “MAJOR” assault to end the bloody siege.

The Kenya Defense Forces said at the time that it had rescued “most” hostages and had taken control of nearly all of the mall. But officials never said how many hostages had been rescued, and Kenya’s military spokesman on Monday was still not able to provide clear details.

“We are yet to get confirmation from what’s happening in the building,” Col. Cyrus Oguna said. Many of the rescued hostages — mostly adults — were suffering from dehydration, Oguna said.

The assault came about 30 hours after 10 to 15 al-Shabab extremists stormed the mall Saturday from two sides, throwing grenades and firing on civilians.

Responding to claims that Westerners or women were involved in the hostage standoff, an al-Shabab commander calling himself Abu Omar lashed out on BBC radio after several British newspapers reported that Samantha Lewthwaite, the widow of one of the suicide bombers in the 2005 London transport attacks, could have masterminded the strike.

“There are some rumors spreading around that say that there have been American, British and other attackers of different nationalities involved,” Abu Omar said. “I can confirm to you that none of that is true, I know that is baseless rumors that have no justification for them.”

Loud exchanges of gunfire rang out from inside the four-story mall throughout Sunday. Kenyan troops were seen carrying in at least two rocket-propelled grenades.

Al-Shabab said the attack, which specifically targeted non-Muslims, was in retribution for Kenyan forces’ 2011 push into neighboring Somalia.

State Department spokeswoman Marie Harf said U.S. law enforcement, military and civilian personnel in Nairobi were providing advice and assistance to the Kenyan authorities. She said five Americans were among the scores of people injured in the attack, but the U.S. had no reports of any American deaths.

Earlier in the day, al-Shabab said on its new Twitter feed — after its previous one was shut down Saturday — that Kenyan officials were asking the hostage-takers to negotiate and offering incentives.

“We’ll not negotiate with the Kenyan govt as long as its forces are invading our country, so reap the bitter fruits of your harvest,” al-Shabab said in a tweet.

In an unprecedented decision, judges at the International Criminal Court excused Kenya’s deputy president from his crimes against humanity trial for a week Monday so he could return home to help deal with the mall hostage crisis.

At a hastily arranged hearing, Presiding Judge Chile Eboe-Osuji said William Ruto could leave on a morning flight to Kenya.

Westgate Mall is at least partially owned by Israelis, and reports circulated that Israeli commandos were on the ground to assist in the response. Four restaurants inside the mall are Israeli-run or owned.

In Israel, a senior defense official said there were no Israeli forces participating in an assault, but said it was possible that Israeli advisers were providing assistance. Israel has close ties to Kenya going back many years.