A temporary UN-brokered ceasefire which went into effect in Yemen at a minute to midnight (2059 GMT) was breached by the Houthi rebels, army sources and local residents said.
The army sources said Houthi rebels and their allies militants loyal to Yemen's former president, Ali Abdullah Saleh, breached the truce since it started, by heavily shelling areas in Taiz, 170 miles south of Sana'a.
The sources added that the Houthi shelling targeted residential areas east and west of Taiz.
The same sources said that the shelling on Taiz came as relative calm was registered on other battlefronts.
Meanwhile, more breaches were registered in two other Yemeni governorates, the sources added.
Houthi rebels and their allies carried out several attacks on areas located in the region Midi, which is located on the Yemeni-Saudi border, 76 miles nothwest of Sana'a and in Mareb, 107 miles, northeast of the capital.
The Saudi-led coalition backing President Abd Rabu Mansour Hadi's government, and the Houthi rebels who control the capital Sana'a, have agreed to the temporary truce.
In a statement on Monday, the office of the UN's special envoy for Yemen said Ismail Ould Cheikh Ahmed had received assurances from all Yemeni parties of their recommitment to the ceasefire.
The Saudi-led coalition announced in a statement that it will abide by the 3-day truce in order to allow humanitarian aid to enter besieged areas, but said that it preserves the right to retaliate to any military movements by the Houthi rebels.
EU's High Representative/Vice-President Federica Mogherini said the 72-hour ceasefire, will allow urgent humanitarian assistance to reach large parts of the population that have been suffering drastic shortages.
"This should be a first step in paving the way for the resumption of the UN-led peace negotiations, which are the only effective means to put an end to the conflict and to find a long-term solution..." she said.
The Saudi-led alliance has intensified attacks in Yemen against rebels since UN-sponsored peace talks between the government and rebels ended without a breakthrough in August.
Early this month, 140 people were killed in a Saudi-led airstrikes on a funeral hall in rebel-held Sana'a. The alliance blamed the attack on "wrong information" from its Yemeni allies.
Saudi Arabia intervened in support of Hadi early last year when the mainly Shia rebels moved on the last strongholds of his internationally recognized government in southern Yemen.
Riyadh fears that the Shia revivalist Houthi movement will give its regional rival, Shia Iran, a foothold in the Arabian Peninsula.
The UN has previously said Saudi-led airstrikes caused the majority of the civilian deaths in the conflict. More recently, it estimated the total number of civilian deaths since the Saudi intervention at over 4,000.
The struggle in what was already one of the poorest countries in the Arab world has led to serious food and water shortages. The World Health Organization has confirmed a cholera outbreak in several areas in recent weeks.
