Media playback is unsupported on your device Media caption Shahzeb Jillani: "A number of suicide attackers stormed the hospital - at least one of them blew himself up"

Gunmen have attacked a hospital in the western Pakistani city of Quetta, hours after an explosion on a bus killed 14 female university students.

Officials say four gunmen were killed during a siege of part of the hospital where the wounded are being treated.

Nurses, hospital security personnel and a senior city official were among the 10 others killed in the stand-off.

An extremist Sunni militant group, Laskar-e-Jhangvi, told the BBC it carried out both attacks.

A man calling describing himself as a spokesman for the group said they were a revenge for an earlier raid by security forces against the group in which a woman and children were killed.

Analysis Balochistan is strategically significant because it borders Iran and Afghanistan. The province is rich in minerals and natural resources - and yet it has remained the country's most impoverished province. Ethnic Baloch nationalists have long accused the central government in Islamabad of exploitation. Thousands of Pakistani troops are deployed across the province to fight militancy. They stand widely accused of abductions and killings of Baloch activists. In recent years, Balochistan has seen more lethal violence by extremist Sunni militants. Groups like Lashkar-e-Jhangvi have carried out major bombings against Shia religious minorities. The group is known for close ties with the Taliban and al-Qaeda.

Quetta is the capital of Balochistan province, which has seen a surge in militant violence in recent months.

The latest violence began when a bomb exploded on a bus carrying female students at a university.

"It was an improvised explosive device placed in the women university bus," police chief Zubair Mahmood said.

Later explosions rocked the medical centre where the students were being treated.

Militants armed with grenades were positioned there and exchanged fire with members of the security forces who rushed to the scene.

Interior Minister Chaudhry Nisar Ali Khan said a subsequent siege ended after security forces stormed the building.

Mr Ali Khan said security forces freed 35 people trapped inside the building, killed four of the attackers and arrested another.

Lashkar-e-Jhangvi Founded in the 1980s, Lashkar-e-Jhangvi is a Sunni Muslim militant group blamed for a string of sectarian and high-profile terror attacks

Banned in Pakistan in 2001 and designated a terrorist group by the US in 2003

The group has ties to other militant networks such as the Pakistani Taliban

It regularly attacks Shia targets, but has also been linked to major attacks such as the 2007 assassination of former PM Benazir Bhutto Profile: Lashkar-e-Jhangvi

Quetta Police Chief Mir Zubair told the BBC that suicide bombers were involved in the attack, with one blowing himself up during the stand-off with security forces.

Mr Zubair said the hospital was a big medical complex and had suggested it could take a few hours to totally clear the area.

Pakistani officials say a senior Quetta official, Abdul Mansoor Khan, who had gone to the hospital to visit the wounded students, was killed in the stand-off.

The violence came hours after militants carried out a rocket attack against a historic home in the Ziarat area of Balochistan, which was used by Pakistan's founding father Muhammad Ali Jinnah.

The house is said to have been severely damaged.

Quetta is the capital of Balochistan province, which has seen a surge in militant violence in recent months.

Some attacks are carried out by separatists and others by Islamists who oppose women's education.

Last month the Taliban killed at least 11 people in an attack on security forces in Quetta.