A Pakistani security official stands amid the rubble of a building adjacent to the Danish Embassy in Islamabad on Monday. (Anjum Naveed/Associated Press)

At least six people died and dozens of others were injured following a massive explosion near the Danish Embassy in Islamabad that officials suspect was caused by a car bomb.

Danish Foreign Minister Per Stig Moeller said the blast in Pakistan's capital killed one embassy worker and a male custodian, and injured three other people.

Speaking to Denmark's TV2 News channel, he said the attack is "totally unacceptable."

"It is terrible that terrorists do this. The embassy is there to have a co-operation between the Pakistani population and Denmark, and that means they are destroying that," Moeller said.

Officials at two hospitals reported at least six people — including two policemen — were killed and 35 wounded. None of those killed were foreigners, but a Brazilian woman working at the Danish Embassy suffered injuries.

Police suspect the blast, around 1 p.m. local time on Monday, was caused by a car bomb. Police officer Muhammad Ashraf said someone parked a car in front of the embassy before a bomb inside the vehicle detonated.

Police officers look at the damage done by the blast. The police say this was a secure area but obviously not secure enough. They promise to beef up security. (Stephen Puddicombe/CBC)

Kamal Shah, a senior Interior Ministry official, said it was not immediately clear whether the explosion was detonated by remote control or a timed bomb, or carried out by a suicide bomber.

Community organization members injured

The explosion left a crater nearly a metre deep and caused extensive damage to Denmark's diplomatic office, as well as buildings around it.

Windows at the embassy were shattered and one of its external walls collapsed, while the property's metal gate was blown open. Footage showed broken glass, collapsed brick and dozens of destroyed vehicles.

Dozens of staff at the neighbouring office of a UN-funded development organization, Devolution Trust for Community Empowerment, were injured by the blast, according to the group's field operations manager. Anjum Masood said most of the injuries were because of flying glass. The building's roof also partially collapsed.

Located nearby, the Norwegian Embassy was closed after incurring "glass breakage," a statement from the Foreign Ministry said. The Swedish Embassy has also been shut.

The U.S. Embassy has told Americans to be extra vigilant if travelling to Islamabad and avoid the explosion site.

There were no Danish officials at the embassy at the time of the attack, the CBC's Stephen Puddicombe reported from Islamabad, as many had moved into a local hotel several weeks ago following the film's release.

While the area where the attack occurred is not part of Islamabad's diplomatic enclave, it is still home to several embassies and heavily fortified with cement blocks and gates.

"So security officials here were quite taken aback by the fact that this bombing happened and they have already admitted they'll have to increase their security to a much greater extent," Puddicombe said.

Pledge to protect

Pakistani Foreign Secretary Salman Bashir said Monday that Pakistan would work to ensure the safety of all foreign diplomatic missions.

The blast left a metre-deep crater in front of the embassy. (Stephen Puddicombe/CBC)

"I think the Pakistani nation feels very ashamed today on incidents such as these," he said.

No person or group has claimed responsibility for the attack. It is the second bombing targeting foreigners in Islamabad in less than three months.

Pakistan has been the site of several large-scale protests against cartoons depicting the Prophet Muhammad that were first published by the Danish newspaper Jyllands-Posten in 2005 and reprinted in Danish newspapers in February.

Al-Qaeda deputy leader Ayman al-Zawahri has called for revenge attacks on Danish targets.

"I urge and incite every Muslim who can harm Denmark to do so in support of the Prophet, God's peace and prayers be upon him, and in defence of his honourable stature," al-Zawahri said in an April 21 video, quoted by IntelCenter, a U.S. group that monitors al-Qaeda messages.

In April, staff members were evacuated from Danish embassies in Algeria and Afghanistan because of threats related to the Muhammad drawings, while Danish intelligence officials warned of an "aggravated" threat against Denmark in Pakistan, North Africa, the Middle East and Afghanistan because of the cartoons.

In March, dozens of Islamists in Pakistan, as well as in other parts of the Muslim world, protested the release of an anti-Islamic film posted on the internet by a Dutch politician.

With files from the Associated Press